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LED Lights: Friend or Foe?
elfdump writes: "In an article (pdf) soon
to be published in ACM Transactions
on Information and Systems Security, security researchers have discovered
that data transmitted through modems and routers can be remotely reconstructed
from the equipment's LED status indicators. According to experiments, their
light-to-information retrieval method is successful even when the light is
captured 'at a considerable distance' from the source. If you want to prevent
people from spying on your data, you may want to tape up those blinking LEDs!"
So I should put big, bulky Duck Tape over my beautiful Airport Base Station? No way! Plus, I get poor enough reception in some parts of my own house, never mind my neighbors spying on me. ;-)
I imagine it would need a lot of things to actually monitor my leds so I'm not worried. Plus, I like too look at them and I won't let them take that away from me :)
rxvt, suse, vi, solaris, debian, java, c, feel the love. #unix@IRCnet, #gimp & #gnome@GIMPnet
I don't do anything interesting with my data anyway. Any corporation/government agency, if they want to go through all that time and trouble, is welcome to whatever they can get. My credit card info gets encrypted before it gets sent, and that's the only thing I do that's worth stealing.
The only surefire protection against Microsoft infections is abstinence. - The Onion
The data is only ip(ppp) data anyway. Which is available on the internet. It won't give you any access to data such as credit card numbers.
You might as well just tap the phone line.
I've read blinking eyes on women in bars from 5 meters for years. Typically the message comes thru...
Busy aligning my non-linear thoughts.
reconstruct the data from the flashing lights??? whatever. That's so ridiculous it's laughable.
If that was possible you would have discovered a spectacular new way to compress data at 1000-1 or better. My DSL modem sends a 1500 byte packet and the light blinks... now reconstruct that packet for me from that single blink... I don't think so.
I wonder who is going to be the first company to release a LED mod to stick on your modem to give random flashes of light( or gimmick it to appear as if you are getting tottaly different data)
what if we went LED mad, covering our gear with hundreds of flashing flickering lights :) - ok lame attempt at first post....
Reminds me of that flash light I got when I was young, with a litte button-switch to do Morse code... Maybe we could all sit in front of a modem and do some IP over flashlight things...
I'd rather be sailing...
At one time I worked with what I thought was a highly paranoid CIO for a manufacturing company. He had custom-made black plastic covers made for every modem in the modem pool (this was waaaay back) for this very reason.
I tried not to think about it but he was convinced that eventually someone would create technology that would re-construct the data transmission based on those LEDs.
If he's reading this (and he knows who he is), you paranoid sod, damn you for being right. *grin*
My sigs always suck.
Wow, that's impressive. I've always wondered why they don't use incandescent bulbs for these applications (tiny flashlight bulbs, the downsind I guess is heat and power consumption). I wonder if manufacturers will switch to something like that to lower the maximum flicker rate. Then again, someone might be able to use the dimming of the light to collect the same data. That makes me wonder, I wonder if those home networks that run over the electrical wires could be tapped by observing any light in the house.
Why aren't we told when editors moderate our posts?
Yeah. If the lights on my switch are any indication, I'm getting about 20bps throughput on my network. Last I checked, the LEDs simply indicated activity, they didn't represent the binary pattern of data going through the ports or any other pertinent information.
...where the main character, in fear of his computer being Van Eck phreaked, redirects output from a decryption program to turn on-and-off his scroll-lock key in morse-code.
--Quidquid latine dictum sit, altum sonatur.
I can see the light
Therefore, I can access the router/switch. Maybe I have to break some glass cabinet first..... but that is probably about as noticeable as putting a great big frigging light detection source right in front of the glass cabinet.
OK, so I can see the lights, therefore I can access the device. Can you think of an easier way of accessing data than blinking LEDs?
Ok, so by sensing the LED, you can tell that transmission took place.. So what? The LED's don't indicate the data pattern, just the transmission pattern.. You can't tell a 1 from a 0 by looking at the LEDs..
It makes more sense to SQID the CRT from a mile away..
The REAL jabber has the user id: 13196
What you do today will cost you a day of your life
The light on your modem flashes when you're receiving data. It's no more telling than that.
Ah! So thats why that bloke was busy covering up all the LED's on the plane with tape...
;)
New spy device?!
ibm defaced my slashdot page! :'(
slashdot: where everyone yells sarcastic metaphors to themselves to understand the issue
It makes quite a bit of sense if you think about it. Audiophiles have been using optical output for years (essentially just an LED and a bit of fiber optic cable). What really caught me off gaurd was the distance they were able to capture the data from. Apparently for some, they found they could capture data from "at least across the street".
Almost makes me wish someone cared enough to spy on me so I could prevent it (Duct tape to the rescue!).
Beez
Monday is a horrible way to spend 1/7 of your life.
I'm thinking their talking specific model of hardware or something. My crappy USR modem sits under my desk anyway. But regardless, is this like packet sniffing, but more.. 'light sniffing' or eh.. I dunno. Anyways, what they going to steal of my IP_masq network? My dad downloading p0rn?
Can all fish swim?
Just put a tiny capacitor on your Tx and Rx LEDs.
It's a hoax anyway...
I'm a 2000 man.
Well, it could happen, but seriously. Would anyone want to spend months and more than ten thousand dollars just to steal my credit card number? Anyway, I'm not even sure it's possible. Prove to me that the blinking lights are synchronized with the hard drive. Hell, when it works a lot, it just stays on all the time! How do you want to get data from that??
Strange that they say such detection does require little apparatus.
The article looks real, but is probably about 5 years too late. I don't know of many people who use external modems. As for routers: the theoretical upper limit is 10Mbs, so my 100Mbps network is safe.
My blog
If true, this is one of the neatest hacks i've heard off. Still, it's hard to imagine that you could get that much info, I mean, lights don't blink all that much. Still, they say they've done it. perhaps there are fluxes in the LED's too small for the naked eye to see or something?
I knew I should have heeded this warning:
ACHTUNG! Alles touristen und non-technischen peepers!
Das machine control is nicht fur gerfinger-poken und mittengrabben. Oderwise is easy schnappen der springenwerk, blowen fuse, und poppencorken mit spitzensparken.
Der machine is diggen by experten only. Is nicht fur geverken by das dummkopfen. Das rubbernecken sightseenen keepen das cotten picken hands in das pockets, so relaxen und watchen das blinkenlights.
Woman: So how do you explain the pr0n you've downloaded?
Man: What pr0n? How do you know?
Woman: With this (shows him videotape). I've been taping the blinking lights on your router!
(having not yet read the article) the premise is unlikely since most LED's on front panels are designed to stay on for longer than the actual activity lasts - in order to present useful information. If there was a one-to-one correspondence between the data and the LED - it would usually appear to a human viewer as an always-on-but-dim LED since the blink-on time would be so short.
To put it another way - there's a buffer before the LED.
-a.e.mossberg
What an appropriate article... Now we will have to change the old Blinkenlichten so as to protect our information...
k enlights.html
ACHTUNG! ALLES LOOKENSPEEPERS!
Das computermachine ist nicht fuer gefingerpoken und mittengrabben. Ist easy schnappen der springenwerk, blowenfusen und poppencorken mit spitzensparken. Ist nicht fuer gewerken bei das dumpkopfen. Das rubbernecken sichtseeren keepen das cotten-pickenen hans in das pockets muss; relaxen und watchen das blinkenlichten.
From:
http://www.tuxedo.org/~esr/jargon/html/entry/blin
Telcos have alot of dark fibre in the States. Most people assume that's optical fibre...but it's actually moral fibre.
I was reading another slashdot story (I think the one about gpl violations), and I saw a business add in the middle of the post! I was like, "WTF"? I was really scared for the future of slashdot... but after reloading and checking some other stories, the add was gone. So, am I hallucinating, or is someone playing with the slashcode and, more importantly, is this something we'll actually see in the future (please say no... please say no...)
Preparing to lose karma for a noble cause...
F-bacher
James Tiberius Kirk: "Spock, the women on your planet are logical. No other planet in the galaxy can make that claim."
even if it did work, wouldn't it be easier to just find some other method of stealing the information? Who the hell would want to sit there and reconstruct the data sent from blinking lights?
.02
Just my worthless
Say you're routing 10 mbit/s To read the data from your led, you would have to be able to register 10 million "frames" of led capture every second. And that is supposing that the led is actually capable of blinking this fast (which I think it's not).
Now, if it was a modem running at 300 bps, then maybe.
Forget the iPod for piracy, just take one of these LED readers and use it to copy data off hard drives by reading the blinking hard drive LED on the front of cases! Imagine the possibilities! Next: LEDs a violation of the SSSCA...
I can only think of one way this can happen. If someone wires up the LED's so that they are hooked directly to the transmit and receive wires so they do actually blink out the bits. Then one would need to send data slow enough so the LED (and receiver) can make out the individual pulses. In this respect, stupid=yes, impossible=no.
Or like usual, I could be just blowing smoke out my ass...
But I'm looking at my calendar and it appears that April 1st is nearly a month away yet.
Hmm. I like having my desk next to a window, I bet you could see the LEDs on the switch and DSL modem from outside. So someone could be "Loughry/Umphress Phreaking" my data xfer.
On the other hand, the DSL connection is on an exposed box on the back of the house. So there are probably easier ways to do the same thing...
BTW, I made a mistake, I meant a modem, not a hard drive. Thought I'd say it before somebody started throwing insults at me for not reading the article. :)
Does this mean I'm going to have to gouge out my own eyeballs or risk violating the DMCA when I go for job interviews and see the lights on the companies' hubs?
What is this world coming to?
Karma: Excellent Birds (mostly as a result of listening to Laurie Anderson)
Check the list of old stories for the details of the new adds that are being implemented and the subscription system you can use in order to avoid them.
The current poll is also related to these new adds.
-- Erv Walter
I'll just put my modem upside down...that way, everything will transmit backwards...
Certainly every man at his best state is but vapor
The light blinks ON when data is going, OFF when it's not. Might make a nice indication of when there is data, but not what that data was.
That's about like seeing the patterns of red and green traffic lights and claiming you can deduce the type of cars on the road.
"None of the Lan interface cards tested, including 10mbit/s Ethernet and 16mbit/s Token Ring Adapters, were found to broadcast any recognizable data. However the most interesting part of the article maybe where it discusses the implications of ATM DES encryptors that have LEDs that blink on the basis of the unencrypted data, hence you could use the LED to read the data.
I know, I've thought the same before reading the entire .pdf... But hey, before saying it's a hoax, go read what you're talking about!
I know it sounds crazy, but it seems to be true!
At least, it's easy to fix this security problem... Where have I put that damn duck tape?
To do this with an LED would require that the LED be actually driven by the data signal. Most of them go on at the start of the packet or byte and go off at the end, they don't go on for 1 and off for 0. So, you might be able to do a little traffic analysis, but you would not be able to recover the data.
Bruce
Bruce Perens.
My switch blinks steadily when I'm doing 100 Mbit switched transfers. There is NOTHING that can be determined from this 2 baud blinking. They're probably talking about old analog modems which run slow and tie the LED right to the TX and RX lines.
On all the new g4 towers (I'm not sure about the others..) the power LED glows and fades. Why not adapt this to other LEDs? That would make it harder to scan, and also make your stuff more 'mod'. Who actually needs to see the LED blink for every bit that goes though your NC or modem? As long as I see there's something going on back there, I know its (usually) working..
Let's assume you've got a slow connection on your average modem and you're running your dialup at 33Kps. This means that you're looking at having that blinking light going through on-off cycles every 1/33000 of a second if you can read the data accurately.
Considering the quality of your average LED inside the modem, I'd be amazed if they can blink on-off distinctly more than 100 times a second. Anything faster else would blur.
This conspiracy theorist should concentrate on finding meaning in radio waves from space.
The lights on my switch indicate activity, they don't flicker to the beat of my bits. Even if they did, there'd probably be too much static and other interference on them to reliably deduce data from them. On hubs it's even worse. You get all traffic flowing through all ports in both directions, try deciphering that! This story is, as far as I'm concerned, major bull and it's not even April 1st yet!
Learn from the mistakes of others. There isn't enough time to make them all yourself.
I have a friend that has a top security clearance working for a big company and he says he's not allowed to have a phone near his workstation because you could use the phone to pick up the frequencies that the monitor is giving off and reconstruct data from that. But at least that seems somewhat viable. Flashing LED's is pretty damn ridiculous, especially since this article is being published in the ACM.
I can see how this might (very small might) be an arguable ability if somebody is only using one network application, but the second you multitask, you've got lights blinking in no meaningful sequence. I fail to see how they can separate pr0n from that 1.4gig VCD being downloaded at the same time.
Good point. Besides, if this is possible, then why in the world are IR transfers so slow? I want 100mbps transfers from ipaq to ipaq over a blinking LED!
Why aren't we told when editors moderate our posts?
Next year I wont put any of those damn blinking lights up on the tree, way too risky. And I dont want to accidently insult the leader of an alien race or something.. And by the way, I guess the same goes for HDD? Can you reconstruct the data pattern based on the terrible noise a HDD is making while it defragments (yet again..) my NTFS partition?
I'm not an electrical engineering expert, so I could have misinterpreted the story. However, as I read it, they claim that for cost saving reasons, the LEDs that just show status are internally electrically connected or at least influenced by the part of the circut that handles the data flow. In other words, the LED is not showing just generic activity, but is actually showing the bit flow.
I'm not sure I believe them though.
-- Erv Walter
Just hide your hub in a teddy bear, noone will point his eavesdropping device on such an innocent toy, would they?
I intend to live forever, so far so good.
Many LEDs have a response time of around 8 nano seconds, which means they can blink roughly 12.5 million times a second. Enough to transmit 12.5 Mb/s of data. If your on a 10Mb network then that's plenty good for the spy. If your on a 100Mb/s network, the spy is out of luck.
-... ---
When the light is ON, the data is "1"
When the light is off, the data is "0"
I don't need large brains to have a good time.
Someone must be ingesting an illegal substance when concocting this post AND someone else is doing the same when posting it to Slashdot.
;-)
The government has done alot with reconstructing data from electronic emissions. Large sections of the Intelligence community do this type of work on a day to day basis. Interpreting data remotely from the emissions your CRT produce is old hat, but blinking LEDs are just that.
The government may be looking over your shoulder at your email, getting a warrant to bug your keyboard and search your hard drive after seizing your computer, but how many does that truly apply to ? For the rest, it's simpler to generate this type of FUD and cause geeks to become paranoid in the hope that we'll be good
I would have to agree with you on this one. Even if the router were only serving a 1.5Mbit T1, that's still 1.5 million bits per second. I have a hard time believing that an LED can blink fast enough to reliably recreate that data.
"The guide is definitive, reality is frequently inaccurate."
I agree, considering the lights don't blink for each bit sent. All you would know is when the modem is receiving/sending.
Tom
Someday, I'll have a real sig.
...let alone OC-x, would be like trying to drink from a fire hose :)
Besides, if LEDs would blink so well that you can reconstruct the signal with consumer-grade equipment, wouldn't we all be using optical networks by now?!
This is rediculous. It's almost crazy enough to have Katz as a contributor. Where'd they get the idea for this? From that kid in Afgahnistan using his C64 to watch DivX movies?
It really can be done.
For example, in high school, I attached an LED to the output of a radio or microphone (can't remember which) and then aimed it at a solar cell attached to the input of a speaker. And it worked! I'm not sure if the quality was good enough to capture a modem signal, but it was certainly a poor-man's wireless speaker.
If the spy has more sensitive equipment, and if the LED on a modem really is tied to the phone line, then there should be nothing stopping the spy from capturing the transmission and decoding it later.
Healthcare article at Kuro5hin
"+1, informative"? Heh, mods are on crack again.
Have a look into a Toslink digital audio connector some time. It's using a plain old LED to transmit information. It looks to the naked eye like it's on solid, there's no flicker whatsoever. What would you "think" if you saw that? Your gut reaction is totally off base here.
SSH. Enough said IMO.
I don't think we have too much to worry about here. They have proved it to work (supposedly, no evidence) on 56kbps. Most results are for 14.4kbps or less. This is for modems - generally they have TD/RD lights which are direct indications of the RS232 lines, so show data.
NICs, routers, switches, and hubs, tend to slow down the light flashes, or flash to packets, rather than bits. It makes it far easier to see what is going on. An LED would have difficulty keeping up with the high data rates as well (as well as any driver circuits).
It could be possible on a switch that has activity lights for all the network to ascertain which ones have most traffic, and hence gateways/DNS servers, but these things are generally found out in much easier ways.
It seems as if most of the posts before this are from people who didn't read the article, and are claiming it can't be true. RTFA.
Privacy certainly has it's points, but if they want to know that badly where I was surfing, I'd just as soon let them find out for that kind of effort.
Does the RIAA know about this? They might be able to get the courts to ban LEDs since apparently now their music is being distributed via light.
For modifying someone's unsubstantiated "hunch" as informative.
I've seen my lights blink, and I don't think that there's any way
Yes, and I've looked on a CD and I just don't see any data on it.
Here's a paper by the amazing Markus Kuhn (who has done many other brilliant security hacks besides this) showing how CRT display contents can be reconstructed from the light given off by the screen, even when the light is reflected diffusely off a wall. It makes me glad I use an LCD monitor.
I've never complained about content on Slashdot before, with the exception of Jon Katz' drivel.
But this is the dumbest thing I've ever heard. No, data can not be constructed from watching the LED's. Who's the marketing genius who came up with this idea? The only things that could be told:
1) You are connected.
2) You are sending data (maybe)
3) You are receiving data (maybe)
Does anybody really think that those little blinky lights are going fast enough to transmit any data? If so, are you on crack!? The only thing data that isn't transmitted too fast is like a 300 baud modem. And I certainly hope nobody's using that anymore. Somebody probably wrote this crap up so they could get marks on a performance review or something.
Soembody needs to have a bag of STFU and stop posting this ignorant imbecility.
Free cell phone tracking
Basically the diodes interact with serial data transmissions because the same high speed gates used to run the logic circuits power the diodes. This allows "an eavesdropper to recover a noisy analog waveform closely approximating the original data stream" which can then be filtered and converted back into the original.
However not all devices are subsceptible. Anyway, take a look yourself at the paper.
Another vote for "Bullsh*t". I'm pretty certain that the LED doesn't blink for *every* single bit. And what about compression techniques that use phase and so on? You are not actually putting just ones and zeros onto the wire you know.
UNIX? They're not even circumcised! Savages!
You should be in the Guiness book of world records. You apparently have the ability to see lights blinking or modulate at rates in excess of 100 hz.
Going to the movies must be pretty tough on you. Watching all that blank time between frames must be pretty nerve racking. I can't even imagine how terrible television appears to you.
If you read the paper, it is based on some pretty coherent testing and past work by others. I think there would be some peer review before publication of an article. But since you have weighed in with your amazing visual prowess, they should just toss out the guy's work.
From the article: "A previously unknown form of compromising emanations has been discovered. LED status indicators on data communication equipment, under certain conditions, are shown to carry a modulated optical signal that is significantly correlated with information being processed by the device."
Don't expect to see this with your eyes! It's like saying you can't sniff data from a wireless network because you don't see nothing passing in front of your eyes. There are things that eyes can't see you know...
After that, good luck doing the packet reconstruction, parse the IP tunnelling, determine what protocol I'm using, and separating signals from my browser, FTP client, weather ticker, httpd, apt-get and realplayer streaming all running at the same time.
I've looked at many, many modems. Almost all of them have the LED driven by an IO pin on the microcontroller inside them. Assuming the anode of the LED is connected to +5v, and the cathode to the IO pin (this is pretty standard - the pins can sink more current than they can source), the IO pin is pulled low when the controller is in its interrupt handler, talking to the UART.
I have got an extremely old 300-baud modem and a 1200-baud modem, which have the LED's connected to the data lines. It would work on those, but not on most modern modems.
Sorry, but this paper is a complete hoax. Based in truth, but only loosely now.
Panic over folks, peel that sticky tape of your modems and enjoy "das blinkenlichts".
All the discussion of the Coming of the Ads over the past week?
Best Slashdot Co
"When in danger,
or in doubt...
Run in circles!
Scream and shout!"
(Wasn't that Heinlein?)
Anyways, this is complete FUD. You cannot pick out binary packet data from transmit/receive status lights.
Put the tinfoil hats back on and crawl back under the table... er, sorry, your "Fortress of Solitude."
SlashSigTheorem: Humorous, Political, Critical, Constructive- If you have a
This is a PHYSICAL encoding, not something cooked up by them. It's used in a variety of devices. Look it up.
There are other schemes, including non-return-to-zero inverted, and non-return-to-zero space. However these two encoding schemes do not work with absolute values, only transitions from one value to another (ie. from one to zero, or zero to one). There is also Return-to-zero and biphase encoding schemes as well, which attempt to correct problems found in the non-return-to-* schemes. However, NRZ-L is the most simple form of encoding, IIRC.
right, but wasn't this radio signal analogue? With all the equiptment I've had, a light blinks when you send data, and a light blinks when you recieve data. Now, an LED has a fast response..really fast...one reply to my origional post said 8 uSeconds or something. That's pretty feasable, but even if it would blink for every packet you recieved, or even every byte, you still wouldn't know the contents of the bits, or whether it's a one or a zero. I'm still calling BS.
Check out my sysadmin blog!
If this correct please mod it up.
Saying Java is nice because it works on all OS's is like saying that anal sex is nice because it works on all genders.
If you're looking over at your hub and thinking "damn, it's broadcasting all the plaintext on my network" don't freak out so quickly.
This is taken from the PDF in question: "None of the LAN interface cards tested, including 10 Mbits/s Ethernet and 16 Mbits/s Token Ring Adapters, were found to broadcast any recognizable data."
Basically, the data rate of the divice in question has to be quite low to acquire any useful information by analyzing LED output. (Modem / Serial Port devices) So most people don't have to worry about this, and the people who do, hopefully are already quite aware of this problem. After all, TEMPEST was pretty big news.
I really don't think the addition of in-article ads are going to change slashdot in any significant way. Why?
So I say "Bring it on, Slashdot." I'll probably use the site just as much as in the past, ads or not, and I trust the admins to not do them stupidly (ie: pop-ups, etc).
52 Weeks, 52 Religions with John Hummel
If your on a 100Mb/s network, the spy is out of luck.
Maybe not. There is quite a bit of redundancy in most network protocols (predictable headers, checksums, etc) as well as in most languages. It might be possible for the spy to squeeze more data out of the signal.
-... ---
Hmm - April 1st isn't that far off now - maybe this is being prepared to be published then...
-- Pete.
Monochrome - Probably the UK's largest internet BBS
Many types of commodity LED can easily exceed 1.5 million on/off transitions per second.
In a related story, you'd best not go outside your house, as you may be struck by lightning or hit by a falling meteor. At least, if you believe that someone is actually interested in you enough to attempt to reconstruct your data using this method. In fact, if you're actually worried about this occurring, you'd better get a restraining order against that stalker.
Of course, I always wanted a stalker for my very own...
(insert attempt to be witty here)
And your eyes can see how many flashes a second?
I'm gonna say that your eyes aren't quick enough to tell what the hell it's really doing.
The Blaster Master Fighting for Truth, Justice, and Evil Pie since 1979
I just typed "led diode response time" at google. The first link is
here.
-... ---
Sightseeren putting packets in das hand, bei vatching das blinklights!
:-) = I am happy
:^) = I am happy with my big nose
C:\> = I am happy with my OS
That funny. I to sometimes think that if I stare at those blinking lights long enough I would be able to discern a message. I just chalked it up to my familys history of mental illness. But it turns out I was right all along.
I see a lot of responses here from people who are quite certain that it can't be done. If you'd read even the abstract of the report, you'd realize that they've conducted experiments in which the transmitted data was reconstructed by means of studying the flickering of the status LED's. You're as bad as security analysts saying that a system is uncrackable. If somebody does something, then clearly it is not impossible.
Virtue finds and chooses the mean.
Aristotle, Ethica Nichomachea
At least for older style comms devices. The easiest (cheapest) thing for the hardware designer to do is to drive the TX/RX status LEDS directly from the UART lines via a simple buffer/inverter. As the article says, these inveters are high speed devices that can switch at least as fast as the data rate.
Theoretically, you'd get pretty good data reproduction if you clean up the signal from the photo detector using a comparator of Schmitt Trigger circuit. The scope trace from 20 meters away shows this quite clearly.
Good lord.
psmylie's dictionary: Godzillion (noun) Any number large enough to destroy Tokyo
Once again: Maybe you think that the light just "blinks" when recieving or sending data, but how can you tell that it's not actually blinking once for each bit (assuming Manchester encoding) and thus broadcasting your entire data?
The illegal we do immediately. The unconstitutional takes a little longer.
--Henry Kissinger
But with the exception of a work of fiction, in which one character uses the LEDs on a computer keyboard to send information in Morse code [Stephenson 1999]...
Credit where credit is due. Excellent book, also.
Once you eliminate the impossible, whatever remains, no matter how improbable, will be quoted out of context on
I work for a major manufacturer of networking equipment so I know for a fact that this is simply misinformation. First of all an LED is just triggered by an electrical signal coming in on a wire. What is more a blink could be multiple bits coming in on a wire not just one. The real kicker is LEDâ(TM)s now dayâ(TM)s only show a sampling of the actual activity on the wire. I wouldnâ(TM)t start covering those LEDâ(TM)s to soon if I were you. Your monitor emissions are a far more accurate targetâ¦
not to mention the fact that his brain isn't quick enough to tell what his eyes are doing
>>Many LEDs have a response time of around 8 nano seconds, which means they can blink roughly 12.5 million times a second.
... yes led's can go about that fast ... trouble is you can't see an 8ns blip of light... the common thing is to put a stretcher on to make the led light up for long enough to allow you to see it ... don't quote me on it exactly but i seem to recall 10ms being a pretty good compromise for the stretch -- that would limit you to 100Hz. Apparently modem mfg's don't do that, but I would n't be surprised if hub mfg's did. ...I'd bet much more than to create a replica spy-ing hub which could be slipped in.
I've been involved with the design of stuff that does fast gates etc (ns or sub-ns timing)
Another thing to consider, if you want to snarf up 8ns wide pulses from across the room in daylight conditions you'll spend a bunch on the hardware
From the paper:
/*
// sl.c -- a covert channel using the Caps Lock LED.
//
// For Solaris 2.x on SPARC; compile with ${CC} sl.c -lposix4
*/
*THAT* is cool. Bundle it w/ a screensaver that makes the other two lights blink randomly and you're set!
Office dweeb: "Look at this neat screensaver, it makes my keyboard lights blink! Wheee!"
Uber-Geek: *jots down keystroke log from caps-lock LED* 47-46-58-82-85-76-69-83......
I'm a 2000 man.
Over time, you notice that people that read and post on Slashdot are extremely misinformed, narrow minded, and self centred.
There are at least 50 posts now on this story claiming it is a hoax. It's clear from many of these that few have actually read the synopsis at the top of the paper, never mind the rest of it.
It is not talking about 10Mbps communications. It is talking about lower data rate comms, like modems, serial lines, and the like.
It does work, only on a small amount of devices. It is short range. This doesn't make it a hoax.
TEMPEST is at a stage where it is hard to perform - we're talking government/big company level to manage anything impressive or useful. Take a look at this tempest radio site. Neat, but not very useful.
If you have no idea what you are talking about or don't have anything useful to add, keep quiet. Is it just so you can get your karmas up???
ok, that MAY be the case (i don't think it is, but but could be), but it's not really likely that the equipment that will record light flashing at this rate is common, and as many people have said there are better ways to get the data. oh well
Check out my sysadmin blog!
My first reaction on reading the headline was: BS!
:-)
But after reading the article, I think this could actually work, right down to the bitstream level, if the bitstream was slow enough. I don't see it working on a 115,200 bps link, but on anything less than 19,200, it seems realistic.
Unbelievable!
Anyone have a circuit diagram for a receiver? I've got some passwords to hack!
This is just too cool. Poor man's tempest snooping. The equipment to do this is trivial. It looks like you can get started with this in just a few minutes with some Radio Shack parts and an oscilloscope.
However, in quickly perusing the article, I didn't see any detailed description for decoding software, though I would think it would be very straightforward DSP.
Expect to see ads for these within days (popup ads, no doubt).
Just realeased!
PGP for LED.
It's surprising that you can actually construct a real data signal from the LED flashes - I thought that an LED would be too slow to respond to a rapidly changing signal so it would just be half-on all the time. But on page 2 of the report they show an LED emitting light that allows you to perfectly reconstruct a 9600b/s signal. I guess LEDs are rather different from lights based on resistors getting hot; they don't need time to warm up or cool down.
This sounds like a dirt-cheap way to construct wireless links, with no risk to human health (unlike lasers). An LED taped to one window and a $29 webcam in the building opposite could get speeds approaching those of a modem, if you designed a protocol specifically for this purpose. The authors of this paper managed to reconstruct data even without a specially-designed protocol.
A bank of say 1000 LEDs, with a zoom lens at the other end to make sure each one is distinguishable, could transmit *at least* 9.6Mb/s, ie more than a megabyte per second. You could do this by taping a pair of binoculars to your webcam.
-- Ed Avis ed@membled.com
The responses to this article seem to all question the switching speed of LEDs. Even the least expensive LEDs are capable of at least 100kHz operation, with many, many, common LEDs capable of operating at several MHz. Remember, most of the fiber-based transceivers use LEDs, not laser diodes. I've used LED-based 3com equipment over a 2 km 62.5/125 um MM fiber link without trouble. These LEDs (not IR LEDs) were easily able to handle 10 Mbps.
Tiller's Rule: Never use a word in written form that you've only heard and never read. You will end up looking foolish.
If you really cared if someone was stealing your transmissions ... would you send non-encrypted data to the modem in the first place?
I found the bit about the keyboard LEDs far more interesting. A sweet hack.
Well I guess I now know why the ccc (chaos computer club) stopped this, they where afraid their pong tactics would get stolen (read this site, its just a perfect hack)
Easy way for manufacturers to fix this --- just use a low-pass filter (ie a resistor in series and a capacitor to ground). This will remove high frequencies, essentially smoothing out the signal.
R
in >--\/\/\---+---> out
|
=C
|
GND
My neighbor rigged a flashlight to his router and is using it to spam me. Please make the bad man stop.
Saying Java is nice because it works on all OS's is like saying that anal sex is nice because it works on all genders.
Either they take away our blinkey lights and shiney objects
or
Electrical tape to cover up said blinkey lights will be labeled as a circumvention device under the DMCA, so we'll be forced to look at the lights (ooooohhh, blinkey).
(Which is a bad thing because the electrical tap is the only thing holding my 1950's style fins on my tinfoil hat.)
Have you read the moderator guidelines? Well, have you, PUNK? (and I want a Karma: Gnarly option)
just put a one-shot (monostable multivibrator for you EE guys) before all the LED's. that way, each LED will stay on for a few extra clock cycles, but will still indicate activity to the human eye.
concerned sysadmins could even do this as a mod by themselves to an existing piece of hardware with a 74123 IC chip (thats got a few one-shots on it - look it up). then you wouldnt sacrifice the visual aid that LED's are meant to provide in the first place.
Somewhere on this page I have hidden my signature.
I wonder if this can be used to solve the mile issue? You basically have an LED that you focus on and one focused back at you. Essentialy a fiber optic network without the fiber.
There seem to be a lot of people saying this is BS. Their examples are modern DSL/Cable models where the light blinks once for a large packet. I think you may have want to read the article. This only worked on 36% of the devices they tested. The LED has to be connected through logic circutry that is the same as the data transmision circutry just more powerfull to light it up. Not all activity LEDs are hooked up this way some blink on a per-packet basis or with other factors. If you look at the devices tested the most successfull tests were on older modems and slower token ring network hubs. This is very obviously a possible technique to read data. As speeds increase though the feasability drops since the responce time of the LED and the "dirty" circutry degrade the signal into a single blip on the LED. As for security ... unless someone really wants your data I doubt you have to worry.
It's not the flashing of the LEDs, but the underlying modulation,
It will naturally work better, where the LED being examined is Full on all the time. So the power LED, could provide the necessary information...
Be sure to use a low capacitance diode to pick up the light. An old large apature 35mm camera lens focesed on a diode array from a compact disk player detector is a great source of a high speed photodiode. It can povide great bandwidth at a long range. Larger photodiodes have larger capacitance and do not carry enough current in the short amount of time to capture high data rates. A large apature telephoto camera lens has the nessary gain to drive high enough light current to provide high speed detection. Alignement and focus are critical for good signal to noise ratio. Any hardware types want to try it? I have and used a scope to check the current waveform. Many pieces of equipment do tie the indicator lights to the signal and do reveal the data. Other equipment has an activity light (ethernet cards as prime example) because the average data traffic is too low of a duty cycle to provide useful illumination for an indicator light.
The truth shall set you free!
Perhaps there are transmissions coming thru to DJ's via the red strobe LED on the good 'ole 1200's!
maybe with a subscription we can choose to block
the BS stories like this one
Maybe I can use this to find out what the blinking light on my power strip has been trying to tell me all this time...
within large U.S. enterprises with 3rd party providers. I am assuming these edge routers will be in closets anyways. Any other thoughts?
Just record a modem or router and play it very slow
:)
(and try to decode the hidden message).
A funny play for your guests at dinner
Ashtar.
The lights on your modem or switch do NOT pulse everytime that a 1 or a 0 gets sent down the pipe. In the case of a modem, they pulse whenever the controller sends a request to the UART. In between those requests, a WHOLE HONKING PACKET OF DATA IS SENT. Same with a switch - light comes on when a PACKET IS SENT.
Sheesh - think about it for a second. If the light blinked every time the device passed a 1 or a 0 down the pipe, then either your device would be talking about about 10 bits per second (yawn) or the light would be on full time.
-- There are two kinds of motorcycles. 1: German. 2: Crap.
I can backup the whole network by videotaping the front panel of our switch.
.
Let's not stir that bag of worms...
...around 3rd or 4th grade (around 1970-1971 timeframe --yep I'm a genuine "Olde Pharte" who reads /. :), I once built an electronic kit from Radio Shack that transmitted voice, one direction only, from an LED to a phototransistor. LEDs were fairly new devices back then, at least for the average joe to get his hands on them. Military electronics and high dollar commercial electronics had them for a while. Anyway, back to the LED "wireless" voice xmitter, it actually had a pretty good range, about 20 feet or so, but the audio quality was extremely poor, only good for voice, not music. There were no IC chips in the kit either, everything was individual transistors.
External modems cost about $70 - $80 more than internal modems - who the hell buys external modems anymore?
Karma: Professionally Doomed (mostly affected by inability to keep opinions to self)
I have therefore taped up every light in the office, and to be extra sure I randomly switch the numlock, scrollock and caps LOCk on and oFF in order to add soME error to the sySTEM.
Please eXCUSe the caps.
Conversion Rate Optimisation French / English consultant
...black, electrical tape.
...security researchers have discovered that data transmitted through sex and foreplay can be remotely reconstructed from the equipment's moans and grunts. According to experiments, their audio-to-information retrieval method is successful even when the sound is heard 'at a considerable distance' from the source. If you want to prevent people from spying on your data, you may want to ballgag your significant other!
Computational Madness in a round package.
Did anyone bother skimming to the end? They provide an ingenious, if not a little disturbing, application of this. As they point out, the keyboard leds are software driven. They supply code that can blink the keyboard leds at a rate that is not noticeable to the average person, and can buffer keystrokes and feed them out through the leds!!
Write a little trojan horse, get your neighbor to run it, and then sit back and watch what they type...
Is it just me, but if you want to be this secure why would your modems be in a place where people could see them. They should be locked up in your server room or such. If they could see the blinking lights, odds are they could walk up and get information much easier than from LED's.
the trouble with doing the morse-over-led is that the EM from it still can be Van Eck phreaked. This is another "security thru obscurity" tactic, but chances of the phreakers being hip to decode morse is probably good.... it could pass right under their noses and they wouldn't think to consider it was morse.... they'd be too focused on looking for something more sophisticated... can't see the forest for the trees kind of thing.
Right.. Seems that on MODEMS (not LANs) the 'on' of the LED is a baud transition, not a bit marker. Granted, so easy enough to decode Huffmann encoding that even silicon can do it, but still.. I just don't buy this as a serious means of breeching security. It's novel, and it even might work at very low thruput rates, but when you're dealing with fast data rates, the response of the LED will mangle whatever pattern it is trying to represent..
The REAL jabber has the user id: 13196
What you do today will cost you a day of your life
I can't believe how many people have posted to dis this paper!
Did any of you read it?
It's well done research, it carefully categorizes what can and can't be reconstructed and it specifies with some detail the methods used to recreate the transmitted data.
It's god damn good research.
They're not stating that ALL LED's exhibit this behavior, just some lower bandwidth ones.
Although I still highly doubt that any useful information would be gleaned from me looking in my neighbor's window and counting pulses from his MODEM LED while he's browing the internet, a spy agency could very well have the technology to figure out how to do this if the particular device is known to have this problem (or "feature", whatever...)
Read, people, read. That's what the paper is there for you to do, not to just hear the title and claim it's impossible.
Kuhn did not invent this technique, I read about this being doable in Popular Science in the mid-to-late 80's. It's called 'van Eck phreaking' after Wim van Eck, its discoverer. As I recall from that long-ago article, he sat in an equipped van parked outside a building, tuned in on a CRT that was inside the building, and read the contents of that screen right off his. I think I was about 12 or 13 at the time, and this was the coolest thing I had ever heard of-- in fact, it made such an impression on me that "kinda like van Eck" was the first thought that crossed my mind when I read the posting on here.
Here's some info about the van Eck phreaking method.
~Philly
Great if RF and EM can't be monitored.
This is a very useful ELint. tool, but it assumes that line of sight to the LED is practical, and Radio Fequencey & Electro Magnetic methods are unavailable. Reading directly off a users monitors is not practical, as the data may be moving via a non displaying program (ie FTP). I cannot see any 'general case' usage of it however as even shielded TWP sheds RF and can be monitored remotely.
Score: -1, Offtopic
For those who are having trouble reading the germanized parent post, please refer to his handy translation reference:
EuroEnglish
The European Commission has just announced an agreement whereby English will be the official language of the EU rather than German, which was the other possibility. As part of the negotiations, Her Majesty's Government conceded that English spelling had some room for improvement and has accepted a 5 year phase-in plan that would be known as "EuroEnglish": --
In the first year, "s" will replace the soft "c".. Sertainly, this will make the sivil sevants jump with joy. The hard "c" will be dropped in favor of the "k". This should klear up konfusion and keyboards kan have one less letter.
There will be growing publik enthusiasm in the sekond year, when the troublesome "ph" will be replaced with the "f". This will make words like "fotograf" 20% shorter.
In the 3rd year, publik akseptanse of the new spelling kan be expekted to reach the stage where more komplikated changes are possible. Governments will enkorage the removal of double letters, which have always ben a deterent to akurate speling. Also, al wil agre that the horible mes of the silent "e"'s in the language is disgraceful, and they should go away.
By the 4th yar, peopl wil be reseptiv to steps such as replasing "th" with "z" and "w" with "v". During ze fifz year, ze unesesary "o" kan be dropd from vords kontaning "ou" and similar changes vud of kors be aplid to ozer kombinations of leters.
After zis fifz yer, ve vil hav a reli sensibl riten styl. Zer vil be no mor trubls or difikultis and evrivun vil find it ezi tu understand ech ozer.
ZE DREM VIL FINALI KUM TRU!!
On projection, a light would be shone through this track onto a photosensitive plate (hell it could've even been a solar cell of some sort). This would generate an electrical signal that, when amplified, created the sound for the film.
I'm old enough to remember seeing some of these films in the theater. Sometimes the film would get misaligned in the projector and you'd be able to see this track. Looked like a buzzing string turned sideways.
This is also why when you see an old film that's been spliced you see the cut before you hear the "pop" in the soundtrack. The sound is read in a different part of the projector, "downstream" of the image.
AMCGLTD.COM. Where cats, science fictio
From what I understand, if they want to reconstruct the data, they need to be able to see the LEDs? Well, they could save alot of time and pick up a $10 pair of binoculars and look up and to the left slightly and view my monitor instead...
Of course I realise that this method could be used to rebulid more sensitive data from more important sources than my computer room at home. Which is great and all, but I don't know of too many data centers or server rooms that have a window view. Which means that their equipment would need physical access. And if anyone can walk in to a server room with the necessary equipment to sniff this data out, well the administrators have bigger problems than flashing leds and the culprits might have an easier time with more conventional means.
of "-1 Didn't Bother To Read The Article". The number of people in this thread who posted and clearly did not read the article is astounding. We need some way of making everybody actually read the article and then start the thread over again. Sheesh.
....To do this with an LED would require that the LED be actually driven by the data signal. Most of them go on at the start of the packet or byte and go off at the end, they don't go on for 1 and off for 0. So, you might be able to do a little traffic analysis, but you would not be able to recover the data. True for some devices but not others. Please read the article. It's quite clear about where this does and does not work.
reminds me of Cryptonomicon. Yeah, that's probably why Cryptonomicon is one of the references in the article!
The LED's don't indicate the data pattern, just the transmission pattern.. It depends on the equipment. Many older serial devices do indicate the data.
I call BS on this one... (Score:2, Informative) Uh, OK. Trying reading the article. And who modded this up?
Tempest (Score:4, Informative)
Yeah Right (Score:3, Interesting) After that, good luck doing the packet reconstruction, parse the IP tunnelling, determine what protocol I'm using, and separating signals from my browser, FTP client, weather ticker, httpd, apt-get and realplayer streaming all running at the same time. OK. Maybe you read the article. But this is just silly. Any good packet analyzer like Ethereal will do all this.
Anyways, this is complete FUD. You cannot pick out binary packet data from transmit/receive status lights. OK. Try reading the article next time.
The light blinks ON when data is going, OFF when it's not. Might make a nice indication of when there is data, but not what that data was. Once again. Read the article. Some things work this way. Some don't.
I would have to agree with you on this one. Even if the router were only serving a 1.5Mbit T1, that's still 1.5 million bits per second. I have a hard time believing that an LED can blink fast enough to reliably recreate that data. Read the article. Your T1 CSU/DSU probably isn't going to drive the LED at 1MHz or more but the LED is quite capable of switching at up to 10MHz.
That's pretty feasable, but even if it would blink for every packet you recieved, or even every byte, you still wouldn't know the contents of the bits, or whether it's a one or a zero. I'm still calling BS. Read the article.
Another vote for "Bullsh*t". I'm pretty certain that the LED doesn't blink for *every* single bit. And what about compression techniques that use phase and so on? You are not actually putting just ones and zeros onto the wire you know. Read the article. The external modems which are vulnerable are transmitting data from the RS-232 side of the modem which has very simple encoding. This is clearly explained in the article.
Wow. We get a nice, well written article with lots of specifics and details about exactly which devices were tested and which leak information, all the way to including comparative graphs of received optical signals, and people call BS on it? I suggest the folks making "tin foil hat" jokes invest in a different type of head gear: reading glasses!
I've glanced at the article, and it seems like a lot of hot air: lots and LOTS of background and diagrams on LED technology, but relatively little detail on how LEDs could betray the data stream in current, modern equipment. Most current data transmissions around a PC occur in heavily encoded form (usually amplitude AND phase modulation). So there is no cable (other than the serial port cable) that you could just splice an LED into and simply read the data stream out. You would have to inject the LED somewhere into the device electronics where the data stream bits are flowing in decoded, truly serial fashion. Why bother, if from a firmware perspective it's much easier to toggle an LED control bit on at the start of a logical data group (packet or whatever), and off when you're done processing it?
The reflection of your monitor, on your eyeballs can be captured too. So, you need to wear a black velvet hood, which covers your head, monitor, modem, etc. so that the evil powers don't collect your top secret crap.
"Would it kill you to put down the toilet seat?" -- Maya Angelou
... would be to use the equipment to read out the contents of the hard drive by reading the flashing of the HDD LED.
Apple built a platform for their ideas, Google built one for everyone's.
no way in hell can they do that, it's incredible that such crap can be taken seriously.
Yes, you are allways putting ones or zeroes.
...because I recently installed NetLED on my Linux box.
Unlike commonly recommended by ergonomics people you should always work in a windowless (sic!) room...
Use The Source, Luke!
Read the parent article again - this is not Van Eck phreaking.
Kuhn is looking at recreating the displayed image based on the intensity of the *light* emitted by the monitor, not the signals from the electronics generating that light. He has done this and it's frighteningly good quality - look at the images in his paper.
He postulates that this could allow the display image to be recreated even for a Tempest-shielded screen in a room with the curtains drawn.
The world has changed and we all have become metal men.
...of my long-gone phreaking and phrauding days. Here in .de it was still safe to bluebox and card calls because the entire was analog at that time and tracing had to be done by hand - certainly not something the german telco would do on a regular basis if only fraud was the crime. Well, i used to know some guy who was a security risk in that matter - before dialing someone or using a card with him in 3way, you had to kick him out or something - he could just recognize DTMF tones with his ears. Prolly not as sophisticated as a LED-to-bitstream hack but it still jumps up in my brain while reading this.
+++ath0
First they take away my command line and replace it with windoze. Then they take away my sexy jet-engnine-spin-up sounding RLL and MFM hard drives. And now no blinky lights?!
Sure, I can leave behind the days where troubleshooting Ethernet required a resistance meter, and when you could hear the memory counting up, and when a goddammed power switch was a goddammed power switch, but now I have to give up blinky lights? What is the world coming to where a computer geek can't proudly behold his array of blinky lights!?
Where's the joy? These evil led sniffing bastards simply must be stopped, that's all there is to it. I'll 3DES the signal going to the LEDs before I resort to covering my beloved LEDs. Duck tape be damned.
An appropriate value will slow down the transitions enough without interfering with the fascination of staring at a blinking light. That means it's working, you know?
+5:offtopic,but anti-American
This really shows that you cannot be paranoid enough. That's it, I am ordering my tinfoil hat today.
Seriously, who would've thought about this? Certainly not me. I'd never thought that an LED might actually represent the state - I merely figured it's activity in general.
An 8 nanosecond pulse is therefore 125 Megahertz (1 Gigahertz divided by 8). So the theoretical limit is 125 Mb/s, not 12.5.
if that were the case, the divice that is blinking, and the device that is reading the blinks would need to share some kind of clock information. 1 1 0 0(binary) would look the same as 1 0 (binary) if I didn't know the duration of each data pulse.
It amazes me how many people posted responses
to this article along the lines of "bullshit it can't be done" without even reading the freaking paper!!
"/. needs a RTFA mod"
The sad thing is that typically the most read early posts are the least informed due to the fact that they skipped the actual step of checking the source first
---"What did I say that sounded like 'Tell me about your day?'"---
Actually, now that I think of it, that must have been what all those big clunky lights were on ST:TOS. Networking of the future!
Free unix account: freeshell.org
The uman eye can differentiate individual pulses at up to 45-55 hz (depends on the person.) After that the LED will appear to be solid. After that, increased speed will only make the light appear slightly brighter until about 70 hz or so, at which point your eye won't be able to discern any difference. So looking at the lights is pretty much pointless.
Keep in mind that this does NOT mean that impulses above 45-55 hz will appear unchanged as freqency increases. Images will simply blend together. This is why you see an increase in quality at high frame rates in quake.
-- Minds are like parachutes... they work best when open.
Could this be a way to create a poor man's fiber optics?
I'm no hardware hacker so I'm not exactly sure what might be involved in doing this, but if the average LED can push out data this fast, it seems like a good poor-man's fiber, or a poor-man's point-to-point wireless connection...
Reading 26 pages incuding diagrams in neatly formated pdf style can`t be that hard, but for those "No way....can`t be done" types who probebly when living a couple of hondred years ago would have said the same thing when invited to come and look and a presentation of an airplane.....
I will cut and paste a list of devices on wich they found what they call "class III behaviour" (led gives away "the" data)
- All but one of their tested modems (out of 13 14400/v32 and other slow external modems)
-Cisco 4000 IP router, Fast Serial TD indicator
-Cisco 7000 IP router, Fast Serial TD indicator(out of 7 wan-devices)
-WTI POLLCAT III PBX Data Recorder, PBX Input A, B indicators
(whatever that may be)
Now wait with running into your server room with a roll of black tape (I guess whe one most vocal one of the "cant be done" camp will now be the one shouting the loudest) and read the really juicy part:
4.3.3 Reverse Engineering of Devices. It appears that some types of data encryption devices, in particular standalone data encryptors and modems with built-in link encryption capability, may emit optical signals in unencrypted form. Figure 6 is a detail taken from the Installation and Operation Manual for the Paradyne InfoLock model 2811-11 DES encryptor. The InfoLock 2811 is a standalone DES (Data Encryption Standard) link encryptor of the type used by financial institutions to encrypt data on their wire transfer and ATM (automated teller machine) networks [Paradyne Corporation 1985]. The figure shows a portion of the data path between the DTE connector (Data Terminal Equipment?the side of the encryptor that connects to a computer) through the encryption function, to the DCE connector (Data Communications Equipment?the side that connects to a modem). The DTE, or red side is unencrypted; the DCE, or black side is encrypted [United States Department of Defense 1987]. It is clear from this diagram that LED indicators on the TXD and RXD (transmitted and received data, respectively) are on the red side of the InfoLock 2811.
Want to know more on their testing methology, read the article ans start contributing to the discusion or just take my word for it that they didn`t do the same kind of research that has lead to the discovery of the morpheus "vulnerbilities"
While 56K seems awfull slow, if anyone here has spent time in a mainframe data centre you will remember that there is a lot of legacy kit out there which is still performing usefull work.
Many old terminal-to-cpu systems use 9Kb links to transmit banking counter terminals to the host machines, etc.
In this case it would be trivial to decode the un-encrypted info they contain.
It is already a ludicrous idea not to have blacked-out blastproof covers on datacentre windows (for disaster reasons), but if a wake-up call is required then hopefully this is it!
Now you don't even need to waste your own bandwidth downloading your pr0n. You can just aim your little LED detector at your neighbor's LED's and get his pr0n.
Not to comment on the initial post (I'm not an EE, but I'll still refer the author to page 5, paras. 2-3 in the article to see if that answers his question), but are people mod'ing based on titles only? This poster asked a serious question, and gets a "troll" metamod. Huh?
I am going to assume that the light blinks when the line is high. Considering thats 100% of the data passed to the other side of the pipe you now have all the data on the indicator light. I don't know if you could pick up any data from a full duplex network or how messed up it would be but half duplex isn't even much of a stretch of the imagination.
"You can now flame me, I am full of love,"
IIRC many fibre technologies are 'laser diode' driven....
Similar sort of thing to CD players.
In high school (okay, over a quarter-century ago) a buddy of mine made a simple breadboard circuit that let us point a phototransistor at the data LED of any modem in the 32-modem timeshare bank and observe the data on an adjacent TTY. Of course, this was a whopping 110 baud with the occasional 300-baud Hazeltine 2000, but it did work. Like a champ.
This is crap. I worked for a router/hub manufacturer, and those guys don't flash the LED every time a bit passes by. They usually flash it every so often, if a packet has gone by. Note the word "packet". There's no conceivable reason why you'd want to waste your very valuable embedded processor time breaking down packets into bytes and bits to make the LED flash more accurately.
What do you learn by even seeing a flash every time a packet goes by?
I'd really doubt that any HW manufacturer is stupid enough to flash an LED every time a bit passes.
Then, you also need to be able to consider the response characteristics of LEDs. Most IR transmissions systems are decidedly limited in the bandwidth that they can pump through, and that's in a system dedicated to pumping it through. I'd highly doubt that the lower-quality LEDs used for displaying packet movement would be capable of keeping up with your average 100Mbps router.
This thing must be an early April Fool's joke.
You can now take the little aluminum hat off your hub.
Why are you letting these clowns ruin our country?
Why on Earth would you worry about somebody peeking in the window or sniffing with a tempest receiver, when you're already broadcasting your signal across kilometers of open wire?
That stuff about receiving high frequency waves from CRT's and stuff is also described in The Cryptonomicon (Neal Stepherson). They called it Von Eck Phreaking. Don't know if in RL it is called that way... but hey... He took it even to a further level: he claimed (in the book, prolly not realistic) that you could receive the high frequency waves from memory chips and thus could even phreak on laptops (i.e. watch the video memory)... Ah wel...
"Ford," Arthur said, "you're turning into a penguin. Stop it." - Arthur Dent talking to Ford Prefect Hithikers guide
luckily i always have my curtains closed (no.. i can't stand the light!!! (in dodgy horror film voice)) unless you can read through thick curtain material im safe from MI5 finding out about all my h4>0ring (j/jk.. honest!)
{TheT3chfreak}
RTFA
They found "type III" behavior (LED state reflects data state) in only two Cisco routers of all they tested. Most modems DID exhibit "type III" behavior, so tape up the remote management modem lights, but no need to tape up each LAN card.
Anyone can intercept the light from my blinking leds and derive the encrypted data all they want. For anything terribly important, I use encryption.
I suppose an ISP couldn't encrypt all the data through their modem banks, but if any of their customers were using encryption over those modems, it'd be secure.
It doesn't make sense to me why traffic lights on a network device would blink for every bit anyway. Why not just on a per-packet basis?
-kidlinux.
Every one should read Neal Stephenson's Cryptonomicon, where they read someone else's screen by intercepting the radio waves coming off his computer. They scanned for the video card signals, and found the horizontal and vertical sync on the monitor. They could see the screen, but not modify anything. Anyway, its a really cool book. READ IT!
Did you read the article? LEDs can reliably pulse at 10 MHz, which is 10baseT speed. I used to have a Netgear hub that did indeed have an LED directly connected to the data line, it flickered but quite faintly. And driver circuits that run at network speeds are no problem - how did they build the network electronics?
...phil
"For a list of the ways which technology has failed to improve our quality of life, press 3."
Now the MPAA can sue the hardware manufactures for violation of the DMCA, as the blinking leds are freely broadcasting all those pirated movies for all to recieve. LOL
While I think that it would be ridculous to intentionally switch the LED for each transmitted bit, it might be possible for any LED connected to the same power supply as the Ethernet bus interface to modulate due to an inadequate power supply. Thus, you might pick up slight modulations in the LED in step with the Manchester encoded signal put on the Ehternet bus. The bus interface draws more current in the positive logic state, causing the power supply voltage to drop slightly.
Down 6db at 20hz. It'll it still blink prettily, but no data.
http://www.angelfire.com/ca3/marlowe Better a smartass than a dumbass.
There is no way you can convince me that those LEDs are precise enough. Except by eavesdropping on my traffic. ;-)
Anyhow, anything important transmitted via my hub (with the blinking lights) is encrypted, so I don't think I need to worry.
Do any of you EEE's out there know the switching speed of most el'cheapo LEDs?
It seems to me, in order to get a pattern off any LED it'd hafta switch intensities VERY fast.
100 million times per second on a 100mbps network... or even 56 thousand per second on modems. That, to me, seems extremely fast for the cheap LEDs that would be put into an indicator light. Maybe not, but in my own personal experience I tried building a 'strobe' out of Radio Shack LEDs.. it didnt work very well because once i got to a speed aplicable for a stobe, it was just a blur of light.. no definite switching
Otherwise you'd be a Fool not to take it seriously.
Just my 0.02 euro.
Trainee BOFH -- Just give me your username & password
A lot of networks are 100Mbps - an LED would not be able to keep up with this. LEDs can pulse at 10Mhz, but this is pushing them to the limits, and it would not be the same simple task as before. They themselves say that theoretically it is possible. I'm not sure, but 10baseT actually changes state at a higher frequency than 10Mhz. Also, the driver circuit it likely to be one transistor. They will use the lowest price part. This may not like operating at such high frequencies. The network side of any device needs to be of higher quality than status LEDs, HUI, anthing like that. And yes, I did read the article, thanks.
There are two ways to put in an LED to show when a device is transmitting or receiving. One is to tie it to the transmit or receive enable/detect signal, IF there is any. The other is to tie it to the data line. In that case, the LED may be blinking right along with the data, although too fast for the human eye to see. It looks like it is on continually, but the signal could be recovered with a fast enough detector. This depends on the LED turn-on/turn-off time; if it's 8 nS (pretty common), a 56K modem would be easy to pick up. ADSL or cable modems at a few MHZ would be sending out a clear signal; I'm not sure if there are cheap optical detectors that will work at those speeds, but there are expensive ones that go into the gigahertz. 10MHz ethernet signals would be "blurry" but with a good detector, a fast ADC, and some signal processing you could recover them. With 100MHZ ethernet, no data could be recovered.
But before you can do any of that, you have to be able to _see_ the blinking lights. If someone can get into your wiring closet and focus an optical detector on your hub, it would be a heck of a lot simpler to just connect the network sniffer by cable. The real hazard is if the blinking lights are pointed out the window -- that's an unusual location for a network hub, switch, router. or server, but it's quite likely your business has some desktop computers with the back towards a window and the LED's for the NIC and modem cards visible from outside, so a telescope in a van parked across the street could, in theory, extract the data. For instance the receptionist's computer is probably oriented this way; it probably isn't worthwhile for someone to go to this much trouble to find out what a receptionist is up to, but if the NIC is showing data flowing to and from other machines on a shared network cable, better stick on a bit of electrical tape...
Okay, before all you blurt out the obvious by saying it is not possible, read the articles. It is possible under certain circumstances.
It comes down to how your devices react to incoming and outgoing data. Some devices will pulse out the contents of your data packet, while others will just blink your LED on whenever a packet is passed through. This can yield totally different results. One is that they can reconstruct the information. The other is that the only thing they can see is that a packet was just moved.
This is a great example what the academic pressure to publish results in. How they managed to expand a topic worth, maybe, four pages to twenty-six pages is beyond belief. Where were the reviewers?
Signed,
an anonymous electrical engineering professor
Damn, the data is encrypted...I can't understand what this led is trying to say!
The story , although presented as a scientific
paper, has some interesting points. They devide
between class II and class III devices.
Typically class II devices are showing flashes
or blinking lights (whatever) which are linearly
related to the ammount of traffic being transported
though the device. There is no possible way that
one can snoop e.g. login/password combinations
from lets say a used bandwidth logging.
Typically class III devices show more life data,
the most vulnerable devices of course the ones
which show a blinking LED for a transported 1
and swithed off LED for a transported 0.
To my knowledge i can't think of such modems
or routers or whatever who show LED activity
on a binary basis.
To be more specific, the two authors classify
for instance all analog 9600 and 14400 baud
modems to display life data. That part of the story
must be treated as a hoax.. Anyone who is into
the older modem technology knows that
the 9600 and 14400 baud speeds are obtained
by modulation through a carrier signal.
So to extract a binary bitstream out of a video
camera logging of blinking modem light is
impossible. The story differs when the same
modems are applied to send/receive faxes.
The cisco 4000 and 7000 routers with a serial
TD indicator are supposedly also class III vulnerable devices. I think thats only valid
again if the LEDS show a binary bitstream.
Robert
Your eyes can't discern discrete changes past, say, 24 Hz (movie frame rate). Data is modulated in the LED in pulses that match the data rate. So to your eye, it appears to be solidly on. To a sensitive solid-state photoreceptor, the changes are discernible (according to the article, at rates up to 10 Mb/s).
Frankly, I'm amazed this wasn't determined to be a problem a long time ago. This is indeed a tangible risk, you naysayers. Passively sniffing a box is a much more subtle way of eavesdropping than cracking open the box or plugging in a new MAC. That flashy data center with the big wire-mesh windows and cipher lock might want to think about some opaque-ish drapes.
FYI, The duty cycle of a standard LED is greater than that of the data passed along by a 56K modem. What does this mean? It means that the LED cannot turn on and off fast enough to represent the information going across your phone wire. I would have to see the specs on the specific LED that was being used, but, I would venture a guess that the baud rate would have to be well below 300kb to make this possible.
Well, laser emitting diodes are obviously able to do this many many times faster, as your average fiber line has a bandwidth FAR exceeding the @10Mbps that seems to be the consensus that the LEDs that we're talking about . Is there a relatively simple way of hacking together a Point-to-point wireless system that uses this? What kind of distances and equipment are involved?
...the NSA has been doing it for 20 years.
but I actually skimmed over the article, which states that it could be useful up to 10Mbps. Since I've got a 100Mbps connection to my modem router, this shouldn't apply to me, right?
WRONG!!!!!!
Wrong because the modem router (probably 56Kbps) is the critical point. Also wrong because even if an LED is showing the data stream on a 100Mbps link, it's still possible for the data to flow at a slower rate, even the rates they mention in the article.
What I found extremely cool in the article was that it explained how a KEYBOARD could be modified to exploit the scroll lock LED to transmit keystroke data to an optical capture device. Another possible exploit is to mod a keyboard so that an IR LED is installed inside but beside the scroll lock LED (leaving the scroll lock LED intact); the emissions would probably still be detectable but not by the human eye.
Problem with using optic wireless stuff is that you have _real_ ambient problems. In your average office you have rather a lot of flourescent emitters (which will introduce pulsed noise at 50/60Hz). Similarly daylight etc can have a major effect on your SNR. ;).
Line of sight can also be a problem (think clouds/rain etc) which tends to make RF a better prospect.
It's possible, and has been done (somewhere else in this post is a link to a laser point to point communications system) and who knows, it might even catch on one day
The telephone line is analog, also. I don't know how modems are designed, however, so the LED could flash either the analog signal of the phone line or the packet-by-packet flash like that on a network hub. Which type of signal goes to the LED is probably a design decision made by the modem company.
Healthcare article at Kuro5hin
I saved $600 on a brand new computer monitor just after I realized all I had to do was watch the LED's on my MODEM to surf Slashdot!
...to put some tape over K.I.T.T.'s LEDs. Wouldn't do to have some bad guys overhearing their private conversations.
Michael Knight, that is... But it is him posting, right?
--
"I'm surfin the dead zone
In the twilight, unknown"
Required: wee thing between device LED connector and LEDs which subs for original pattern one that spells "Fuck off you nosey bastard".
1) Remove tinfoil from head. This will allow the FBI to read your thoughts and aliens to control your thinking, but this is LED SECURITY!!
2) Place tinfoil over LED (a) at a 45-degree angle reflecting the light towards LED(b). Poke a hole in the tinfoil to allow some light through.
3) Take tinfoil and make covering/receiving/reflecting receptor on LED(b).
When LED(a) lights, any scanning devices will be mercilessly confused by the colighting of LED(b). The secret bat equipment will be useless!
4) Make sure you put tinfoil back on head.
I completely agree that this is a hoax or other misguided article. Many people are pointing out that and LED does have the bandwidth to carry lots of data, which I would agree with, and that LED's are currently being used to carry signals of various forms. As BandMan points out, however, the LED on a modem or switch/router isn't making any attempt to encode the data. It is ONLY telling you when there is a packet being either sent or received. How you could reconstruct the pattern of one's and zero's in those packets is beyond me.
Keep passing the open windows...
Everyone needs to relax a little bit. WHO CARES!!! If somebody is that serious about stealing your data, then they are going to get it some how! Trust me, I can probably find easier ways to steal your data then capturing blinking LED's. The fact that everyone is arguing about this is ludicrous.
So, any bets as to how long it takes for something like this to appear on "Alias". For some reason, I was reading the article and kept thinking of Marshall constructing a device that read the LEDs of a modem.
Of course, "Alias" has those mystical tempesting devices that live only in Hollywood, but still, it sounds like one of their ideas.
Fortran programmer...oh yeah. Array math for life!
Vanity kills
" Have a look into a Toslink digital audio connector some time. It's using a plain old LED to transmit information. It looks to the naked eye like it's on solid, there's no flicker whatsoever. What would you "think" if you saw that? Your gut reaction is totally off base here."
No I agree with him! And remotes too! There's no way remotes can work. I press the button on the remote, and I don't see any light. Infrared? Nah I don't believe that any electrical device can see things that I can't!
This has got to be the most ridiculous post I've ever seen. No shit you can "technically" read off the blinking LEDS but who in the fuck is going to do it? Jesus christ. The next post will be, "slashdot hackers have discovered that one can pick up the phone in ones house and listen in on the conversation." Amazing.
your netgear would have to be(at a minimum) a Class III device, and have the highest quality(most expensive)LEDS before someone could even begin to use this against you.
somehow I doubt any home modem would meet those requirments.
The Kruger Dunning explains most post on
Maybe the people on the Nebuchadnezzar in "The Matrix" use this as a training exercise for learning how to watch/read those green screens of binary information - first they start with 56k modems, then they graduate to 10 MB hubs....
How long do you think before Cringely gets a big'ol LED and tries to establish a high-speed connection from his house out in the sticks over the hill into Santa Rosa?
Sure, it takes awhile to learn how to read it...
But after awhile, I just see Blonde here, Brunette there, Redhead over there...
This is one of those things that the casual user/individual doesn't need to worry about at all but, those ultra-parinoid government agencies may decide it is worth the worry.
Light-beam communications is very feasible and has been used for years. For slow speed RS-232 connections (and even for 10mb network connections) I can see how they can pull this off fairly easily. With good optics and fast-enough electronics you can read the signals as if they were morse code from quite a distance.
It would also be pretty easy for manufacturers to defeat. Just place a small capacitor across the LED, it would charge enough to hold the light in an active state across several bit changes providing a useful indicator light without acting as an unintentional conduit for information. My guess is that the better built equipment already does this because it will make the LED brighter.
Someone's going to pirate all my porn from my network.
Certainly you don't think that the best funded, most brainy intel outfit in the world didn't think this up already, maybe over two decades ago? *grin* Given that the NSA manages to soak up the biggest and brightest in the computer and communications world, even before people realize that someone is a bright one, don't you think this has been done before, maybe for decades???
I still think that Tempest operations are more likely.
Trivia fact... The State Farm Insurance Company's world headquarters building in Bloomington, Illinois, is built to defeat tempest operations. All windows through out the facility are darkly tinted and have embedded micro mesh wiring to keep EM emissions from leaking out. Their safety system for securing their outgoing data lines and satellite communications center is built, well... lets say it's built better than anything you might find on all but the latest military facilities.
The SW tower used to house the mainframe systems. Because of this, that tower has even additional EM and Visual shielding. The rooms are all set back from the windows, with an interviening metal sandwich/composit wall (making all outside windows a hallway, unlike the other three short towers and the high rise exec tower). Floors as well in this tower got a treatment of EM shielding, and all floors are raised on purpose with data drop floor panels for routing cables. Cable trunk guides and tubeways are EM shielded as well.
'Carpe vitam globis!'
There's no wrong way, to eat a Rhesus...
Applied-math.org isn't putting thru the article.
No other mirrors listed on this page == no reading the article anymore.
-- Ender, Duke_of_URL
Yea, I think I can remember my lights on my modem would sometimes stay lit for a few seconds at a time, who knows how many 1's could have flown by in that time frame..
I would imagine that the person who is bored enough to actually want to try this would need to know the exact line speed to sync the lights with the packets or something. I dunno, im still doubtful this works but oh well, I dont have the time to debunk it =P
Sure, and I'm the queen of England. And even in the extremely unlikely event that you're telling the truth, looking at the insides of a modem isn't going to tell you anything about how the modem's LED works. I've been to NASA's Johnson Space Center a couple of times and have looked at the insides of a few rocket engines. Therefore I must be an expert!
I have a SupraFaxModem 14.4. I noticed a few years ago (when I was using the modem daily) that if I send a stream of NUL bytes down the line, the LED looks noticeably different (brighter) than when I send regular data. And if I send a break signal, the LED lights up solid for a second or so (however long the break is). The LED most certainly is correlated to the actual bits being sent down the line.
What do you think is pushing all that data down the fibreoptic cable, a candle and Cowboy Neil?
"I'm not impatient. I just hate waiting." - My Dad
The Cisco 4000 and 7000 *Fast Serial TD indicators* show evidence of Class III optical emanations.
:)
But sure, by all means, go ahead and start shutting down all of your 4000s and 7000s.
When a router passes data, the led doesn't modulate on the bit level. Stop being so stinkin paranoid. Sheesh. The sky isn't falling.
Wish I had an oscilliscope right now. I've suspected the telltale LEDs on my new external modem... but haven't had a way to check since I currently don't own or have access to a scope.
"Alcohol, Tobacco, Firearms, and Explosives" should be a convenience store, not a government agency.
Don't you all think modem and network equipment makers should have thought of this a LONG time ago, and made those LEDs blink at a CONSTANT rate when there is traffic activity, as opposed to the rate the bits pass by???
Let's hope CISCO, Netgear, CLynk, 3COM and all the others pay attention to this issue...
Reading Bruce Perens' (UID 3872) post and then CaseyB's (UID 1105) post, my thought process (I swear to you) was:
"Hmm...Bruce Perens is a SmartGuy(tm), and I've never heard of CaseyB. But CaseyB has a much lower UID than Bruce Perens, so CaseyB must be right."
Crazy.
-Waldo Jaquith
thank you :) I love the moderation history though
Moderation Totals: Informative=2, Overrated=4, Total=6.
lol
Check out my sysadmin blog!
In the section discussing how several channels could be separataed from a encompassing optical flux measurement they make the assumption that all of the channels are running on a slightly different clock. They use this clock skew assumption of assist with the decode.
From several years of working at a company that developed multiport serial hardware I don't think this is a totally valid assumption. On all of our boards there was a single master clock that drove all of the UARTs.
This master clock will be divded down inside of each UART to create the baud clock. And this division will allow each channel to skew in quantums related to the baud divisor. *But* at high baud rates the divisor shrinks meaning that for 2 comingled channels instead of a 1-in-4096 chance of a clock skew you only have a 1-in-2 or 1-in-4 chance.
--Rob
I run an open 802.11b access point. My network
is as insecure as it gets. It's good practice anyway
to assume your network is insecure. That's why I use
ssh/scp/stunnel for all my network traffic that
includes a password.
Brings new meaning to this:
Das Komputermachine ist nicht fuer gerfingerpoken und mittengrabben.
Ist easy schnappen der springenwerk, blowfusen und poppencorken mit Spitzensparken.
Ist nicht fuer gerverken bei das Dummkopfen.
Das Rubbernecken sightseeren keepen Hands in das Pockets,
relaxen und watchen das Blinkenlights.
und deciphering das Blinkenlights too?
Absolutely right... Persistence of Vision is what allows us to enjoy television and film. Without it, we'd see the individual film frames being sprocketed along on screen. Film doesn't actually fly by at a constant speed, the sprockets advance the film and hold it momentarily 24 times a second.
I forget now the "retention" length the average eye holds, but it's pretty slow. We can't see the LED flash as fast as it does, and I'll bet the LED has three stages, OFF for no data, DIM (or something thereabouts) for 0 and HI for 1. Probably not something programmed in, but just a result of the data being sent and how the LED is triggered.
RTFA. Off-the-shelf LEDs can reliably switch on and off at a rate close to 10MHz. The experimenters were able to successfully pull data from the T1 interface of a Cisco 4000 router, where the LED is apparently driven by one of the data lines.
...phil
"For a list of the ways which technology has failed to improve our quality of life, press 3."
I remember when I was in the office at Acorn Computers chatting to a guy called Dave Walker. Someone walked up to his desk, plonked down an Acorn PC and said it wasn't working. He plugged it in and watched it for a moment (just the box, no monitor was plugged in). After a few seconds he pulled the top off, pushed in a certain chip (loose memory or something), put the lid on and booted... this time the PC whirred into life properly. When I asked him how he did that magic trick, he told me that when there is an error the floppy drive light blinks it out in morse code. I'd had one of these machines for years and had never known that was staring me in the face!
Phillip.
Property for sale in Nice, France
(Reading the paper shows a footnote indicating the researcher was a student of Seattle University -- just down the road from my house).
Thanks. Before I thought the firewall and IDS system would keep those hacker kids out of my home network. Now I have to tinfoil the windows.
j.
Not if it's a glowing filiment (incandescent) type, anyway. The warm-up time on the incandescent bulb is MUCH longer than the duration of A/C's 60hz crest transition.
Florescent bulbs, perhaps, but the perceived "harsness" of florescent light precludes their use in bedrooms.
Regular LED's of course are designed to do this... oh, wait, they arent!
-Robert
WebMaster:
BinFeeds
XXX Thumbnailed Image Newsgroups but
I'm glad you bothered to at least look up the duty cycle of the LEDs in the equipment. Oh, wait, you didn't!
Not to mention that it doesn't require a full low-to-high cycle, just a variation in intensity is sufficient to decode the data.
Yeah, you can take LEDs and solar cells to transfer sound. Check this link out: http://scitoys.com/scitoys/scitoys/light/light.htm l#laser_communicator
Orange
Um, if they're in your datacenter staring at the blinking lights on your equipment, with enough access to hook up monitoring devices, you have MUCH bigger security problems at hand...
But I need that tape to hold my tinfoil hat on!
Some Fiber Optic equipment uses blinking LED's to transmit information (multi-mode). Technology has since moved to lasers but in older or cheaper equipment LED's are/were used. So as long as the LED is indicitive of the actual data being sent then it shouldn't be a problem to reconstruct the information being sent.
Now maybe we can finally figure out what OS they were using on the Enterprise.
Incidentally, literature fans, Thomas Pynchon mentions this idea in passing in the "Byron the Bulb" section of Gravity's Rainbow.
What is with all this talk about "my modem" stuff. I would point out Lockheed had their hand in this "big" discovery and they don't make modems kids. Just to goes to show you where US millitary budget goes to. Your just one more AI...What you "thought" you were special. Don't worry we're programed that way.
You thought you were special...Don't worry you were prgramed that way.
I'm not sure, but 10baseT actually changes state at a higher frequency than 10Mhz.
You're correct. Manchester encoding is used for all 10 Mbps Ethernets, so the state could change at a rate of up to 20 MHz.
--Mike--
Unless someone has direct physical access to your Class III equipment, they can't read anything in the MHz range. So, those Cisco routers are safe after all.
Direct physical access is often surprisingly easy to come by through either force or social engineering. Many people involved in the crypto field conveniently ignore that all the crypto in the world isn't going to save you if somebody points a pistol at your head and asks you for the cleartext.
Will I retire or break 10K?
The bulb glows because the buld is hot. The bulb don't have the time to become cold in only 1/60th of second. Common lights are not blinking, it takes a few sine wave for them to be hot enough and a few ms for them to become so cold taht they don't glow.
Um, "fuck" isn't an adjective. It's a verb or a noun.
And, isn't the UART inside the microcontroller in "most modern modems"? Doesn't that make Tx and Rx "IO pins on the microcontroller"?
Maybe I'm remembering wrong, but I think there's more to the article than BS.
Virg
First, if the LEDs are on the TxD and RxD paths, they'll blink with every bit, not every packet. By the article's terminology, class III LEDs do just that, and most modems (and a few switches) are set up in class III configuration.
Second, take a close look at the light over your head. If you're in the U.S., it's pulsing at 120 Hz (incandescent lights get brighter and dimmer, fluorescent lights actually go dark and light). Can you actually see them flickering? Not likely. Therefore, is it safe to assume that because it looks like the LED is going on and off at 10 bits per second, that each flash is not a series of on/off cycles too fast for your eye to detect? Again, not likely. In reality, class III LEDs do indeed flash out the data stream, and equipment sensitive enough to discern it (which the human eye is not) can read the data stream.
By the way, to close off the two obvious arguments, in modern modems, the UART is a part of the microcontroller, so the LED can indeed be hooked up to Tx/Rx easily, and in the case of data transmission, even cheap LEDs can cycle in the 10-100 nanosecond range, so the light would merely appear to the human eye to be on full time.
Virg
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Clickety Click
Actually for RS-232 serial a 1 is -5 to -25V and a 0 is +5 to +25V, so it's quite possible the LED is on for 0 and off for 1
Ummmm....
OK, I knew this years ago.
Your computer teacher tells you this in grade school when they say a light bulb is a binary memory unit. Therefore, the transmit LED on your modem is a binary indicator. therefore if you record what comes off of iot you can reconstruct a data stream.
I'm gonna post the next piece of AMAZING RESEARCH right here. If I remove the LED and wire the leads into the microphone port of a tape recorder and press record then I will have a recorded data stream, ready to decipher at my convenience.
Sometimes it's just sad. The amazing thing about this research is that anyone thought this wasnt known.
Ok. Assume the LED has useful information. (Bits, 1 = on, 0 = off and it can turn on and off fast enough for a data line of average speed, i.e. 100meg ethernet)
Based on how much power, minus how much light energy leaves, and the heat generation of the LED (efficiency), how hot would the LED get at 100mhz? 1Ghz? 10Ghz? (or whatever gigabit ethernet bit rate would need to be to cover overhead)
I bet that if someone (not me!) knew the numbers, you'd find that your router would have burned a hole in the floor long ago if they actually modulated at the actual bit rate. Since they have not caught fire yet, I bet you could say that that most devices do not cycle for each bit.
That would make the article interesting but not significant.
Thus, for anything dealing with more modern levels of data transfer (1meg / sec or more) you could assume that the LEDs were not in fact lighting per bit, just because they do not get too hot. However, if the temp is still within reason, then it is still possible. (And back to the speculation in the rest of the responses.)
Making the article interesting and significant.
On a side note, I know that some devices definately do NOT blink per bit. I can watch my cruddy 4 port hub, cable modem, router and LAN card light. Some stuff goes in what appears to be packets or bits (cant tell which, cant see that fast), but the hub blinks along at a steady 3 or 4 blinks per second for data transfer. Definately NOT the same as what shows up on the router lights.
So, anybody know power/efficency/heat of LEDs well enough to ballpark the heat output on a port on a 100megabit router?
- connect the data line to an edge triggered flip-flop
- connect the flip-flop output to a parallel I/O port
- connect the read strobe on the I/O port to the reset line of the flip-flop
- connect the front panel LEDs to a parallel I/O port
Software:In the real-time clock interrupt service routine, read/reset the data activity flip-flops, write the state of the flip-flops to the appropriate front panel LEDs.
I've done this on embedded systems. Having the front panel LEDs under software control, instead of being hardwired, can be very useful. It takes minimal hardware and allows you to do creative things in the software for diagnostics.
Mea navis aericumbens anguillis abundat
Linux would have been useless with the GNU project. Even if the GNU project had never completed their Free OS kernel, the 386BSD branch was a full Free Software reimplementation of Unix. You might have arguably helped the world of personal computing by removing the Cult of Personality focus from feasibility. After all, Linus is easy to love when compared to most grizzled Unix wizards. I almost wish you could, just so I can find out if Stallman would have insisted on GNU/BSD. I doubt it, but I still am a bit curious. Another benefit is that we would not have the WWW as we know it today! And are you really implying that there aren't any Windows nerds? Most "Linux" nerds are just last year's Windows nerds.
An do you really think you could have defeated Jessie Owens?
Comment removed based on user account deletion
I remember how back in 1995 another intern at SGI spent the whole summer trying to figure out how to program the blinkenlights on big SGI/Crays only to find out that they are, in fact, generated by a separate battery-powered plastic unit generating essentually random patterns. It looked like something out of a toystore. Apparently, the serious government customer expects blinkenlights. It aint a supercomputer without the blinkenlights. Is it CM/War games legacy? The same guy previously did successefully write a library to control blinkenlights on a 20-CPU Sequent, though.
Acceptable according to who? "duck tape" is wrong. That isn't what it's called. And it was not "originally" called "duck tape"; it's always been called DUCT tape, because it was created for sealing HVAC ducts. "Duck" tape came about because a) it's easy to mishear, and b) people are illiterate morons who have no fscking idea what a duct is or why one might want to tape one.
Could you not easily hack your equipment by putting an inline capacitor on the annode side of your LEDs? Just a small one so that the light will blink once per packet, not once per bit.
Here is a prime example of blatant illogical thinking on the part of the
o op ing.reut/index.html
media:
http://www.cnn.com/2002/TECH/ptech/03/07/led.sn
Keep in mind I've done embedded modem code, and my primary technical job
at work is to deal with fault situations, including displaying status
codes on LEDs so I'm familar witht he technology and its limitations.
Here's what's wrong with this article:
1) LED's are very slow devices. That means they can only turn off so many
times in a second - on average, 50 times a second. That means *50* baud,
which is about 6 characters in a second. There is no technical way that
these LEDs can turn on and off fast enough to support even the slowest of
modems! It's like driving at 500 MPH and snapping 6 pictures over the
course of 50 miles and saying that you can figure out what's in between
the pictures. Not technically possible.
2) The author makes the assumption that the blinking lights are actually
connected directly to the data stream. This isn't true! One problem we had
with our modems initially is we did have the data stream tied to the
lights. Once the speed of modems edged up (we're talking 9600bps, here
folks, so this was a LONG time ago), the data was toggling so fast that
all we could get out of the status LEDs was a dim glow. So we wrote code
to keep the status LEDs on for a minimum period of time so they'd actually
show up.
3) The author knows nothing about ATMs and their protocols. Even if
internal modems built in to ATMs (to which almost all are internal with no
indicator lights of any sort), having the data stream, byte by byte will
not be a repeatable sequence anyway. There is a trust set up between each
ATM and their servers and no two transactions are identical. The stream is
encrypted. When was the last time you saw any LEDs on ATMs?
4) The article infers that one can even detect network traffic from the
LED. Come on - an LED capable of 50 baud revealing the actual traffic on
even something as slow as 10 megabit network?
5) Most of the LEDs that people see on devices don't display any critical
information anyway. Power status, fault status, drive activity, etc.. is
most of it.
It's asinine things like this that just make me want to scream. They
spread fear, uncertainty, and doubt based on factless speculation to
promote themselves to groups of people who don't know better.
Don't ever believe anything technical you read in the media. It's almost always wrong.
been watching those special uncut/uncensored Three's Company episodes recently? tsk tsk tsk
Thanks for the great example of how some random asshole might want to reach out and make life difficult for a complete stranger. About one in three posts I make here has some kind of DoS type comment like this for a reply. People go to great lengths to break things. If someone nice has done this and published it, you can be sure hundreds of malicious losers with nothing better to do have mastered the trick.
Friends don't help friends install M$ junk.
The response time for a LED is on the order of 10^-9 seconds or less. In fact, many fiber-optic data transmittion systems use IR LEDs to transmit the data. I would not be suprised if you can read a 100MB/sec steam off of a standard green LED. Of course, you would need some fancy equiptment to do so.
--- At my sig, unleash hell.
Damn, we 10MB IRDA/home fiberoptic ubiquity long before we knew it! To bad no one came to market with a receiver....
moto411.com
Lol, i'd like to see them try it on my comptuer, just my desktop one has over 38 leds on, and around it :). i won't go on to my server, it has over 50 :),
Reece,
It is explained in detail. Modems with class III leds do not actually just turn on when activity is present and off when its not. They turn on when 1's pass through so they are actually blinking so fast that you cannot see them as anything but on when data is passing. It is much cheaper to manufacture this way (read the fucking article) and therefore many devices use this method of status indication through leds.
--
WHO ATE MY BREAKFAST PANTS?
to this article along the lines of "bullshit it can't be done" without even reading the freaking paper!!
Stupid idiot, they are saying that IN RESPONSE TO THE ARTICLE. Did you even think before responding? I bet not.
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