Slashdot Mirror
802.11 WiFi Denial of Service Exploit Discovered
CRC'99 writes "The Queensland University of Technology has today announced yet another flaw in 802.11 products. AusCERT has the official statement, noting: 'An attacker using a low-powered, portable device such as an electronic PDA and a commonly available wireless networking card may cause significant disruption to all WLAN traffic within range, in a manner that makes identification and localisation of the attacker difficult.' Nice to know that a simple PDA could bring a WiFi network to its knees."
Seams like the single most energetic use of all our new technology is figuring out new ways to break it.
Always going forward, 'cause we can't find reverse.
Same reason you get someone else to proofread your CV. A fresh pair of eyes will pick out the problems.
weren't they called JAMMERS back in the nice radio-sharks times? Jam the 11 802.11 band frequencies and you have a "DoS" attack...
I wonder if WiFi bridges are also affected by this.
And of course, how long it will take before the manufacturers will be having a firmware update for this. It seems that most firmware updates only add extra functionality to gain an edge over the competitors, but basic stuff like optimalisation is kind of a non-issue. I'm crossing my fingers this will be fixed shortly, but I'm having doubts about it.
The best weapon of a dictatorship is secrecy, but the best weapon of a democracy should be the weapon of openness.
In case of a chain:
It's easier to find a weak link in a chain, than it is to make all perfectly strong links.
In case of a 'system':
It's easier to find a single flaw than it is to build all parts well. (not to mention that all parts must also interact well, and do the job.)
using something as small, cheap and common as a hammer I may cause significant disruption to *all* computer activity within walking distance.
What would be the point of this other than making people made? It would not dystroy data. Also, has it been done by a "attacker" or did they do it themselves?
Because the creators think one way, and the the "other people" think in totally another. Something the creators never thought possible could happen, simply because someone else sees the system on a different angle.
A microwave oven can bring down a WiFi network. You could plug a 110 volt line into an Ethernet jack if you felt like it. All shared media networks require cooperation in order to run correctly.
This could be a huge problem. Let's say you have a business where you have high sales volumes at certain times, with these times determined by unknown external factors (like a stock broker). If your network is down at those critical times, you loose business and money. Now all your competition needs to do is take out your network during one of these critical times, and all your customers will turn to them.
Wifi networks _require_ cooperation to work. When the protocol says I am not allowed to send now, who can enforce it? I have to admit that tricking everybody else into believing that the channel is in use when it is actually free is an elegant way of disrupting the network, but you could just as well send short blips whenever someone else tries to transmit a packet. Only software which you control stands between you and the network.
i agree with you,
but considering the fact that the system they are building is important than CV (ust an example), why they don't get what others get in first glance?
I've never quite understood WiFi.
I know people who have dailup internet connections and two or three computers, none of them laptops, but still use wifi in preference to RJ-45. (In fact I know people who connect one fixed computer to it's dial-up with WiFi, cause RJ11 phone cable is ugly.)
It's very fashionable, but doesn't seem to work very well. Everyone I know with a WiFi home network has had problems with it.
That said, the idea of free connections in cafes would be cool if there where more of them...
# cat
Damn, my RAM is full of llamas.
This one has a bit more information.
2 3%255E15306,00.html
http://news.com.au/common/story_page/0,4057,95497
Beware the (sometimes flash) ads.
Go to: http://www.wi-fiplanet.com/tutorials/article.php/2 200071
Good info!
-Imidazole2
this just in...wireless networks are open to a range of attack vectors generally closed to wired networks...competitive interefence leads to signal degradation and loss of service...film at 11
seriously, and i haven't even read the article yet, what could possibly be the news here. i'm imagining that, what, certain tiny packet sequences have a disproportionately large disruptive impact on the protocol by causing extended resets and delays? how is that any different from the recent tcp packet spoofing attacks except in free space?
it would still be easier to get a big antenna and a transceiver and just blanket the spectrum.
move along, nothing to see here.
more information is available in RFC 3580 on the same topic.
Couldn't the same effect also be achieve by a simple spark-gap generator? Granted, this device would also effect all other bands, but has been around for many years and is remarkably low tech.
He who laughs last is stuck in a time dilation bubble.
Would like to buy second-hand WiFi-enabled PDA, preferably low-powered. Please email me at: big.nothing@bigger.com
SIG: TAKE OFF EVERY 'CAPTAIN'!!
Can you say, "cheap microwave oven" ???
/. for HERF.....
The cheaper, the better.
Want to screw your neighbor over?
take the cover off the oven and turn it on.
Just don't be in the same room when you throw the switch, sort of like when the executioner lights up a prisoner in "Old Sparky"...
Pick one up off the side of the road and then do a google site search on
Have fun kiddies!!
I was under the impression that such public frequency devices like Wifi and cordless telephones were forbidden from preventing jamming and also must not interfer with other devices themselves!?
This is the same problem as with LA or VHF radio. Only one device can be transmitting at a time on a single frequency band. This stems from the fact that the receivers have to tune to a certain signal and no two signals are likely to be in the same phase, thus the strongest signal will win. Essentially these devices behave as if they are half-duplex, and well-timed (continuous) collisions will cause the whole segment to come down. This is what happens here. Remember the old coaxial 10base ethernet networks? They were vulnerable to the same thing.
The unfortunate fact here is that there is no cure for this kind of misbehaviour. Old devices likely won't be upgradeable (hence no silver bullet). Multi-band hi-speed WiFi (54Mbit+) is not likely to be affected by this attack, but if they operate in compatibility mode they will be brought down, too. Intelligent access points can lessen the effect of this attack but that leaves the older devices out of the communications.
Essentially this requires quite little work on the part of the attacker since no hi-powered transmitters are needed. That fortunately limits the range of the attack, too. I would like to know if anyone could calculate quick estimates as to the affected area with certain wattage transmitters. Anyone?
"Intellectual Property" should be an affront to anyone capable of independent thought.
CDMA would not solve this problem. CDMA operates the same as 802.11, in that it is a direct sequence spread spectrum modulation. They are different, though, in that 802.11 devices all use the same spreading code, whereas CDMA uses different spreading codes for each device. CDMA is based upon a "base station subscriber" model, where the base station controls all of the subscriber devices - telling them which codes to use, and managing the interference environment. 802.11 is based on a distributed "no node is greater than any other node" basis. Centralized management of spreading codes would require a total re-architecting of 802.11, and would take it in directions that are inimical to the design objectives of the technology.
P.S. I am a member of the 802.11 committee -- I know of what I speak
Yup. In other breaking news, microwave ovens operating at certain frequencies have just been discovered to be an effective DoS tool for wireless networks within a limited range.
Another undisclosed report by the NSA reports that hammers are pretty effective too, though their range is extremely short.
Daniel
Carpe Diem
it's easy to flood a wireless network, when using colision avoidance, if you're the only one not playing by the rules, you can own the network. It's like being on a token ring, and editing your protocol stack, to never put new tokens on, once you get one, Nobody else gets to send. Any protocol can be broken if you have computers that don't follow the protocol.
Anthropic principle: We see the universe the way it is because if it were different we would not be here to see it.
I can't imagine how this got on the front page. A regular 2.4GHz cordless phone is enough to take down a WiFi network. And if you're willing to go with a non-portable solution, a cheap microwave will quite easily act as an on-off switch for the whole network.
I remember vacuum cleaners used to destroy TV reception, so I can't imagine they're good for wireless networking either. Any ideas?
aQazaQa
RTFA. It says that jamming attacks of this sort need a powerful transmitter - not the easiest thing to obtain - whereas this just needs an ordinary wireless LAN card, which is much cheaper and easier to obtain.
Er... What? Correct me if I'm wrong, but aren't PDAs based on a hardware architecture thats not used in desktops? Or at least not in PCs! Unless you count anything with RAM, a proccesor, and a disk as a PC...
# cat
Damn, my RAM is full of llamas.
If a user is trying to get in and sends two packets of unauthorized data within one second, WPA will assume it is under attack and shut down.
The only thing the h4x0r need to do in this situation is send data frames periodically, causing constant shutdowns.
Annoying enought he may be difficult or impossible to find because he don't need to use much transmit power or utilization of the network
This affects WiFi phones as well, based on the AusCERT description of the problem as targeting the physical layer. Good to know before deploying an IP telephony solutions that include a WiFi component.
org.slashdot.post.SignatureNotFoundException: ewg
pfft, we all know the exploit is covering the targets house in tin foil so it can't penetrate
--- [Insert intresting Sig here]
Last time I looked a simple PDA has a 400mhz processor, 64 meg of RAM, a 64k colour screen, multiple expansion sockets and support for WiFi and/or bluetooth.
Hardly simple. You must be thinking of one of those Palm products :o)
Avantslash - View Slashdot cleanly on your mobile phone.
Insufficent spectrum with which to develop long enough spreading codes to both achieve the needed low cross-correlation (from one code to any other code), and still maintain 11 Mbits/sec transmission speed. (note: to achieve 11 Mbit/s in 22 MHz of spectrum, 802.11b uses a complex modulation scheme known as CCK - Complementary Code Keying. While I do not fully understand the math behind this, it seems that CCK is unlikely to be amenable to use in creating families of codes with low cross-correlation properties - needed for CDMA).
:)
IS-95 CDMA, I believe, transmits a few kilobits/sec of voice information in a 1.2 MHz bandwidth, using "standard" DSSS. CDMA works because the coding gain with such a huge ratio of data bandwidth to DSSS modulation bandwidth is much larger than that achieved in 802.11 systems.
If you are willing to drop your data rate to, oh, 200 kilobits/sec in the 2.4 GHz band, perhaps 802.11 could be redesigned to accomplish CDMA techniques.
Still, setting up "point-to-point" RF links between individual end user stations would require an enormous amount of computing horsepower (check out a CDMA base station for comparison). And it would not deal with broadcasts, which would still have to be forwarded to an access point - be recoded for each INDIVIDUAL link to each subscriber it serves - and retransmitted N times, where N=number of users served by the access point.
Other systems actually do use techniques somewhat like this, but rather than code division, they use space division (e.g. Vivato, which uses electronic beam steering to establish point-to-point links with each subscriber station).
As I originally stated, and let me re-state - 802.11 is architected on the basis of an "all stations are equal" approach, which makes an uncomfortable fit with a centralized control design. The committee entertained many, many proposals which included centralized control, and rejected them. There are a couple of straightforward reasons: 1) The RF spectrum in which these devices operate is unlicensed and hence "uncontrolled". A base-station centric design would make it so that no station could communicate at all if that base station were experiencing service-blocking interference. The chosen design, though not completely eliminating this failure mode, is more resilient in the face of such issues. Second, the 802.11 MAC is essentially identical for use in an infrastructure mode (i.e. with access points connected to a "distribution medium", typically a wired LAN) and in "ad hoc" mode (where there are only "stations" - no infrastructure at all). Most people forget about "ad hoc" mode, but the committee could not. Their charter required that it be accommodated.
Your turn
Also, it's easier to find an exploit in an established system. Now we have lots of hardware and available WLAN access points to play about with. It's quite difficult to 'hack' a specification...
This really isn't anything revolutionary. You can take down cell phones in the area that a handheld jammer can transmit. I don't think anyone has ever asserted that low-power wireless transmissions can't be DOS'ed by other low-power wireless transmissions.
Chris -- http://www.bitter.net/
A similar note is that the new Super G wireless routers are using the entire spectrum of 11 channels to increase the speed to a reported 108mbps. It's not an approved standard, but as long as it's not enabled at the factory they are still able to sell them.
If you want to knock out your neighbor's ap just run your Super G router with 108mbps mode enabled.
If you can read this sig - the bitch fell off.
The word is "Lose". You do not "loose" (antonym of "tight") money.
Honey, I shrunk the Cygwin
As a network admin, I would love to have several 802.11 jammers, and plant them all over the building. This would keep people from installing rouge wireless networks.
The upshot is that conveniece and reliability are generally opposing design goals. Things which are highly reliable by definition must be mature (read old) technologies - you can't know if it will run for n years if you haven't run 1000's of examples for more than n years. WiFi is both relativly new and falls into the convenience camp. And until we can be convinced otherwise it must stay there.
Art is the mathematics of emotion
I'm pretty sure factual knowledge is, by definition, off topic for /. so I'm going to have to ask you to take it elsewhere.
Give a man a fish, he'll eat for a day, but teach a man to phish...
I only know about the theoretical side of CSMA/CD, but as far I can see, its an ineherent flaw in communicating over shared broadcast channels.
Few communication channels follow the abstract "shared broadcast" model.
If all devices had and used directional receiver antennas (say, six antennas pointing in different directions with that pick up different signal strengths and determine the source location based on these strengths), we could avoid the problem.
May we never see th
At a recent conference I worked, we provided 802.11b wireless Internet access. Lots of people were complaining about the conenction, so I fired up NetStumbler and noticed that there was an Ad-Hoc node on the same channel and same SSID as our AP.
Evidently, a lot of the "automagic" features on laptops to find and connect to an AP decided to connect to the Ad-Hoc node (in Ad-Hoc mode, of course).
Also I am really of the impression that the existence of an Ad-Hoc node on the same channel as an AP causes severe degredation of the channel throughput. Maybe someone can confirm/deny this.
Anyway, I used my amateur radio transmitter hunting skills to track down the guy stuck on Ad-Hoc mode, including wrapping a cone of aluminum foil around my PCMCIA 802.11b card to give it some directionality. I finally found the guy, asked him to turn off his wireless card. He said he had no idea what Ad-Hoc mode was...
By the way, this attack would be a killer way to distribute a virus at a trade show...I suppose someone could even have a trojan horse AP to do something like that as well.
how come "other people" are soooo smart in finding bugs in the system, than the system creators itself?
Because they never look.
This is NOT a "bug in the system". Being jammable is inherent in ANY radio based communication system.
Just as you can't hear and understand the person talking to you across the room when a pair of people are shouting in your ears or when another person with a similar voice is babbling nonsense at the same time, and you can't read morse code flashlight blinks sent by someone standing between you and the sun, so you can't receive and decode what a Wi-Fi card is sending you when another Wi-Fi card is transmitting "chatter".
The same is true on Cable TV modem signals (where a neighbor's chattering box jams your uplink), on 10-Base Ethernet (where you're all on one coaxial cable and a single chattering device is a constant collision), on broadcast radio and TV (where a nearby signal will wipe out or override and replace a distant one), radar, telephone party lines, hearing (meetings disrupted by the guy with the bullhorn), vision (strobe lights, searchlights, sombody standing between you and what you want to see), and so on.
Jammability is inherent in sharing a transmission medium with an additiona transmitter which is misbehaving, not some "bug" in any particular system.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way