Disabling Wireless Networks?

An Ominous Coward asks: "The University of Florida student chapter of ACM hosts a yearly programming competition for students throughout the state of Florida. It is based on the ACM International Collegiate Programming Contest, and for the past ten years has been very successful, currently drawing a crowd in the hundreds. However, this year was the first we had a problem with wireless networks. We doubt that cheating was the intention, as no one had SSID broadcasting turned off (as far as we know). Wireless networking gear is quite inexpensive now. And while we don't believe it affected the contest this year, we would like to take precautions for future contests. Is there any way to disable all wireless networking in an area about the size of a large lecture hall?"

Comments

Disable Wireless Network

[spector30]

You should put little metal hats on all wireless antennas. That way the aliens can't get at those precious routers.

Seriously, though, you may be able to setup a small microwave source(s) in the vicinity. Though it may not block all signals. It should effectively reduce the usefulness of anything within a reasonable area.

Re:Disable Wireless Network

[FooAtWFU]

But would the FCC care to make any complaints about this interference?

Re:Disable Wireless Network

[tdemark]

I have an easier solution.

A few of these..

One or two of these.

Maybe this or a smaller order.

And a smattering of these.

Problem solved.

Re:Disable Wireless Network

[pbox]

Yeah, just turn on the microwave. Alternatively you can microwave the lecture hall. Added bonus is the exploding humans...

Re:Disable Wireless Network

[itwerx]

Problem solved.

We need a moderation "-1 Idiot".
(Or maybe this is a clever troll? Oh dear... :)

Anyways, if you RTFA, you would discover that they are talking about students potentially using WiFi to communicate amongst themselves (or persons unknown outside of the area).
They're already wired, they're trying to prevent the un-wired from having free reign.

Re:Disable Wireless Network

[Anonymous Coward]

Dammit. Omitted the line that was the whole point of the post.

And a hacked one of these.

- Tony

Re:Disable Wireless Network

[Gilk180]

If it is restricted to the 802.11 frequencies, no.

Re:Disable Wireless Network

[Micro$will]

I was thinking about something like that. Maybe give away free hot pockets and set up microwaves all around the lecture hall.

Re:Disable Wireless Network

[kps]

Microwave ovens generally operate at 2.450 GHz, which only intersects 802.11 channels 7 through 10.

And the humans won't explode if you poke a few holes in them with a fork.

This may be impractical, but ...

[magefile]

Why not use a university computer lab? Then you have total control. Or, take a look at everyone's laptop as it comes in. They can leave the card with you (like a coat check), or, if it has integrated wireless of some sort, let them use a spare desktop or laptop you've brought for the purpose.

Re:This may be impractical, but ...

[foidulus]

Or, take a look at everyone's laptop as it comes in. They can leave the card with you (like a coat check), or, if it has integrated wireless of some sort, let them use a spare desktop or laptop you've brought for the purpose.
That would be a lot of overhead. Are you going to check the specs of every system to ensure that it doesn't have a centrino processor(If someone were to cheat they would have no qualms about switching/removing stickers). I don't know how many powerbook/iBooks they get, but are you preparted to lift up the keyboard to look for an airport card on each one? Plus they could always sneak in wireless cards.
It's much more practical to find a way to disable the networks instead of the cards.

Re:This may be impractical, but ...

[lambent]

Coatchecking ... that's basically unreasonable searching. Unless there is reasonable doubt defined by the college Judicial code or a warrant, no one should have access to your stuff. And how do you even determine what laptop has integrated wireless? Ask politely, and expect the subject to answer truthfully so you can take away their machine? What if someone removes the logos and stickers, how do you tell then?

Also, there's an old saying ... if you outlaw guns, only outlaws will have guns. Or something like that. By taking away suspect equipment, you'll only be rewarding those who are better at sneaking around.

I do agree, however, that using a computer lab so that everyone is on equal footing is probably the best idea.

Re:This may be impractical, but ...

[jeffy124]

agreed. A setup where the host controls the show is best for this situation. I personally participated in the ACM's programming contests during their Fall '01 and '02 competitions, and can give info on the environment they use. (FWIW, we never got past the regional competition either year).

Basically, the contest was staged in a typical university computer lab, and all the machines were using some special image created just for the contest and installed that morning. A log was created of all activity from the rooms being used, and checked later (I think the admin did this via a router or firewall). Any activity other than the network connection required for the submission software got your team DQ'd.

Re:This may be impractical, but ...

[FooAtWFU]

agreed. A setup where the host controls the show is best for this situation.

The advantage of people using their own machines is they have their own environment, their own prefrences, and all the settings which they would like to use. If you're an emacs lover, what would you do if a contest stuck you with vi, or vice versa? What of all the small-time IDEs and editors which are adored by their users (both of them!)?

Re:This may be impractical, but ...

[jeffy124]

You're not constrained to a specific editor. You could use anything the system had on it. Emacs, vi, pico, some Notepad-like tool that was in the desktop (forget if it was gnome or kde), whatever. No special IDEs - just the regular gcc, g++, or IBM's Java SDK were provided and also used on the judging side (IBM was a contest sponsor).

The only real problem regarding editors was for emacs users, especially those used to their own config setup. But - those are the breaks of participating in such a contest. Though it really shouldn't matter much since more people use vi than emacs 2 to 1 anyway. (proof - fourth paragraph)

Re:This may be impractical, but ...

[Anonymous Coward]

It could just as easily be done at a private location. Renting a medium sized sports arena. Freedom of speech is not protected in private establishments. How many times have you gone into a club and been checked for firearms? Same idea.

FCC

[Anonymous Coward]

You could use a transmitter that just broadcasts noise on the 2.4GHz band, but I think you would find yourself in violation of FCC regulations.

Re:FCC

[haydenth]

Is it still violating FCC regulations if its in an unlicenced frequency?

Re:FCC

[Anonymous Coward]

Generally speaking, the FCC tends to frown upon passive radio jammers. The only way to get around this is to make an active jammer that merely replies to the signals it recieves (even if it is replying with garbage).

Re:FCC

[AlphaOne]

Is it still violating FCC regulations if its in an unlicenced frequency?

It IS licensed spectrum! Or, more accurately, about half of it is. Amateur Radio is assigned a portion of that spectrum as a "licensed operator" and you cannot harmfully interfere with them.

In addition, you can't exceed the limitations given in FCC Part 15.

Re:FCC

[Anonymous Coward]

I'll be waiting for the FCC to come and shut me down.

Re:FCC

[Technician]

Better yet is to use the basement ballroom. The cement is a great attenuater so outside connectivity is mostly gone. Run netstumbler and project the results for all to see on the screen. Investigate anything picked up. Basicaly a no very visable we are all watching, no cheats here. This would not violate any FCC regulation.

All you can eat solution

[aztektum]

Provide all you can eat frozen burritos and fill the room with microwaves

Re:All you can eat solution

[lizrd]

That's a different kind of DOS attack. Usually it stands for denail of service, in this case it has to stand for Density of Scent.

Can you even imagine the smell of a lecture hall full of hackers recently goreged on frozen burritos? Yuck.

In the can

[crstophr]

Make everyone work in a shielded metal, enclosed cubicle and change the name of the contest to:
"Code in a Can"

--Chris

Re:In the can

[harrkev]

At my job, people who do clasified work do this. It is called a "vault." And the radio reception in there is terrible. No music :(

yes there is a solution...

[ForestGrump]

just run a microwave oven in the back, a few cordless phones, a few rouge APs
hopefully that is enough noise to kill most networks...

or just make it very clear: NO WIRELESS NETWORKS. Walk around with netstumbler and a directional antenna. After a few people get antennas pointed at them, the networks will stop.

-Grump

Re:yes there is a solution...

[bentfork]

or just make it very clear: NO WIRELESS NETWORKS. Walk around with netstumbler and a directional antenna. After a few people get antennas pointed at them, the networks will stop.

I think that is a good idea. You could log all traffic, and the location within you lecture hall with 3 modified linksys 'G' wifi routers. Record the information, and afterwords ban the offenders.

IMHO I am sure that if you though some people were cheating that you could demand their laptop/etc and get their wep key. You could then (I assume) decrypt the logged data and prove that they were sending around answers. ( or better, prove that they were not sending answers...)

Re:yes there is a solution...

[Olathe]

Any good encryption (like SSL) with spoofed MAC addresses would stop you from being able to read much or link transmissions to specific people.

only one way to be sure...

[ubiquitin]

... use a high-signal white noise generator.

AirJack

[.@.]

Simple. You simply forge the MAC of the access point (or just use the broadcast MAC), and spew dissociate/deauthenticate frames. As long as you're transmitting, nobody in range of the transmission can associate with an access point.

This was the basis for the AirJack tool.

If I recall

[Jahf]

There was a project that would broadcast tons of fake SSIDs in an attempt to obscure the right one.

Given that principle, would it be possible to create a box that intercepts and responds with junk to any 802.11 packet it encounters?

Not sure, but I've given it thought myself when giving a class where everyone is sitting there checking email (when you give a 3-day bootcamp on a subject everyone starts to drift -if- there is a distraction ... I don't care if they want to check, but they can get up and do the checking in another room ... 1 distraction leads to 2 and on and on).

You don't necessarily need to -block- 802.11 traffic if you can make the existing networks worthless by giving junk back to the 802.11 clients. Perhaps masquerading the MAC of any AP you find active would be enough?

Re:If I recall

[alatesystems]

I don't care if they want to check, but they can get up and do the checking in another room ... 1 distraction leads to 2 and on and on).

One leads to another, then ten, then more,
And no one buys anything from the store!
So no one gets paid and they can't make more,
The posse breaks up and that closes the door!
DON'T COPY!! (DON'T COPY THAT FLOPPY)

Click Here before you mod me down. It is the FUNNIEST video ever. Email me if you want a copy of it; I can dcc it on irc or something to you.

Chris

Linking

[AnwerB]

I think that the links provided could be more relavant.

Re:Linking

[Spamlent Green]

who modded this offtopic? the parent is right. the links are totally useless. I had hoped to find a story about the problems they encountered, and instead see a big cisco ad.

Low Priority

[gmaestro]

What we really need to do is figure out how to disable wireless phones in an area about the size of a movie theatre or concert hall. Perhaps something slightly less lethal than a shotgun.

Re:Low Priority

[SecretFire]

I see no problems with the low-tech "shotgun" approach.

Re:Low Priority

[jonadab]

> What we really need to do is figure out how to disable wireless phones in an
> area about the size of a movie theatre or concert hall. Perhaps something
> slightly less lethal than a shotgun.

The lethality of a shotgun depends on what kind of ammo you use. For example,
if you load your shotgun with rock salt, it's a lot less lethal than if you
use buck shot.

Re:Low Priority

[Anonymous Coward]

Use the shotgun and copper shot to create a subdermal RF shield for the offender, and then insert the cell phone within the RF shield through one of several orifices.

Re:Low Priority

[ares284]

I've seen a few cell phone jammers already. Check them out here. Says it can block them up to 15 meters (approximately 49 feet).

Might be enough to stop people in theatres if you're lucky. Although we all know that shotguns would really be more effective...


-Ares

DoS attacks for 802.11 networks

[samgrover]

There are several 802.11 denial of service attacks explained in this paper

Speaking from experience

[Cecil]

It's simple. Someone at OSConf in Toronto this year had no trouble taking out the entire WLAN with a laptop broadcasting in Ad-hoc mode on the same channel, same SSID.

Idiot. *mutter*

Re:Speaking from experience

[Halfbaked Plan]

The more interesting question is wether there was a way to detect who was doing it.

You will have more luck just monitoring it.

[Blaze74]

Most of the other posters here have mentioned ways to flood the network with bssids, etc. Chances are this will not work since the bssid's will be chosen by the cheaters. You will probably have more luck running kismet or some other sniffing tool to monitor the wireless network. Then you can see if anyone tries to use the wireless network.

I'm not sure but...

[pr0c]

Ask my neighbor, the bastard seams to always screw up my router but thats alright, I'm within range of his router with a "Linksys" SSID with no encryption and no MAC filters that has a 3 meg cable connection.. I just borrow that =P I throttle my connection at 2.9, no need to be a dick about it.

TV kills the net

[Anonymous Coward]

Wireless AV transmitters kill WLAN. Uncompressed analog TV signals eat bandwidth like no tomorrow and these gadgets use the same ISM band as WLANs.

Make a jammer

[in10d]

Did you try to implement this 802.11 WiFi Denial of Service Exploit Discovered Not So Long Time Ago?

As far as I understand, this would block all 802.11x communication in the area.

Make sure it blocks cell phones too...

[Anonymous Coward]

People could always hook up their palms or notebooks via bluetooth to their phone's data connection. If you're only checking for Wi-Fi signals, you won't catch cell phone cheaters.

Bigass transmitter

[billcopc]

Just get a humongous 2.4ghz transmitter to squash all the rogues on all channels.

Or hire a bunch of evil nazi unabrow dykes to slap cheaters silly.

Disable Phones? Copper Mesh!

[clbyjack81]

What we really need to do is figure out how to disable wireless phones in an area about the size of a movie theatre or concert hall.

Actually, that isn't that hard, you just have to plan for it in the consruction. Before attaching drywall to the studs, put a layer of this mesh on the studs. That will block pretty much all RF based devices from reaching their towers.

Simple

[CMU_Nort]

Just seal everyone inside of a Faraday cage at the start of each contest.

The Matrix

[gchan]

E.M.P.

EMP's

[Jorkapp]

A good solid EMP should disable all wireless networks in the vicinity*

*as well as all computers, electronic gadgets, and vehicles built before 1980's

The trouble is generating one. You can use either:

- Very large capacitors, or...

- A nuclear device **

**With a nuclear device, you will not only disable all wireless networks, electronics, and vehicles built before the 1980's, but all humans, buildings, and organic matter for a very wide radius. No FCC complaints, but alot of DoD complaints will result.

Re:EMP's

[Wog]

Wouldn't a large EMP disable cars built *after* 1980, but not the ones before? Gizmos and all...

Here's an idiotic idea...

[Anonymous Coward]

Pick up a thing called a telephone and punch
the right numbers to get in contact with the person
who runs the wireless network on your campus. I'll
bet if you ask him nicely (and palm his/her hands with silver)
, you can get the wireless access points for that
hall turned off.

*GASP* What an amazing idea!

magnetron

[LordMyren]

a very big magnetron should do the job adeuqately.

Another solution...

[Propaganda13]

Don't use computers. Use a pen and pad. Good programming should be done before it's entered on a computer.

I do like the idea of just saying No wireless networks. Monitor, if you catch them - humiliate them, then ban them for a couple years.

Re:Another solution...

[ForestGrump]

If caught, make them lick your toes.
Make a video of the himulaiton available for download.
That should be enough to keep them from cheating.

-Grump

Cheap Solution

[g0bshiTe]

Bring a few wireless phones in the 2.4 ghtz range, they should create enough line noise to kill any connection.

WiFi is just the beginning... it's hopeless...

[Anonymous Coward]

I hate to be the one to bring this up, but it's mostly hopeless. The *only* way to really block everything is to control the hardware and software they're using 100% OR monitor they like mad (very unlikely to be practical).

Here are some possibilities:
1) WiFi is often at 2.4 GHz. But how about 802.11a at 5.8? Or variants of 802.11b that run at 900-some MHz? For that matter, custom equipment can work on nearly ANY frequency. Try monitoring that!

2) Bluetooth is another protocol, and with new high power output modes, it can have similar range as WiFi. How many bluetooth scanners are out there that actually detect "hidden" bluetooth transmissions?

3) Cellular. New 3G networks are very fast. GSM's EDGE tops out at 384 Kbps (note that it is practically slower, but still 50-120 Kbps isn't bad) and looks just like a regular GSM call which is illegal to actively block. The latest renditions of CDMA also support data to 144 Kbps, and look pretty much like a CDMA call to an RF monitor.

4) Other proprietary technologies from power line transmission protocols (try catching one of those guys!) to infrared and beyond can be virtually undetectable.

So I vote for either control the machines or monitor like mad or - gasp - lay out strict rules and *trust* the participants. Technical blocking measures just won't work if people are very determined.

Look in the latest issue of mobile pc magazine

[osho_gg]

I just read the latest issue of mobile pc magazine (no I am not affiliated with them in any way) - they had an article about signal jammers, which are getting much more affordable to own. They are effective in blocking a range of signals - including cell-phone, wifi etc. depending on type of jammers you get. You probably don't need to own it but just rent it - so it may be really affordable.

Osho

Use a VPN

[ayf6]

Use a VPN who's concentrator forces the client to send a disabled bit for all other interfaces on the box. Cisco's VPN software can do this and you can modify it so that it also sends other flags such as a version or key that the end user probably wont be able to discover in time to duplicate with other compatiable VPN software. This would prevent you from using the wireless interfaces on a box.

Re:Disable Phones? Copper Mesh!

[Paulrothrock]

Aha! So that's what they did to my house! No wonder I can only get reception outside!