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Can Faraday Cages Tame Wi-Fi? 145

Posted by Zonk
from the heeya-heeya-back-wifi-back dept.
mrraven writes "An article at TechWorld discusses the increased need for wireless network security. One possible solution to this problem is the use of building-wide Faraday cages to block the wireless signal from 'leaking'." From the article: "Small installations of RF shielding don't have to be expensive, and the basic concept of a Faraday cage can be extended to all kinds of small everyday objects. Leather wallets sandwiched with a conductive RF-shielding layer can prevent RFID scanners from reading personal information implanted in everything from RFID-enabled access control cards to some credit cards; they're widely available for as little as US$15. For those favoring a more DIY route, several Web sites have information on how to make an RFID-blocking wallet with duct tape and aluminum foil."
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Can Faraday Cages Tame Wi-Fi?

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  • by Cygfrydd (957180) <cygfrydd.llewellyn@ g m a i l . com> on Saturday August 26, 2006 @02:27PM (#15985495)
    So this is essentially a giant tinfoil hat for your office? Will it stop the voices as well?
    • by mrraven (129238)
      When I originally submitted the article that my last sentence was something like: "giant tinfoil hat for a building or hitech deadbolt lock for the 21st century?"
    • Re: (Score:3, Funny)

      by tocs (866673)
      No,
      I think the idea is to keep the voices from leaking out.
    • by Dachannien (617929) on Saturday August 26, 2006 @02:55PM (#15985603)
      Will it stop the voices as well?

      No, but it will keep the voices from using your neighbor's access point.

    • by shmlco (594907) on Saturday August 26, 2006 @03:18PM (#15985673) Homepage
      I want the tinfoil wallet.

      BTW, I can just image the "scare-the-consumer" infomercials for those. "Anyone just walking by can steal your entire life! Stop them now with our high-tech disposable Super-TF-Wallet! Just 3 easy payments of $19.95 and you...."
      • I got news for you, those stainless steel chain-maille butchers gloves go for $180.00; a wallet isn't going to be less because it'll take about the same amount of chain-maille plus the leather internals, I'd guess we're talking $200-300 for one that looks halfway decent. You could do something a bit tackier by sandwiching the aluminized mylar used to shield circuit boards inside a wallet for about $60.00 retail
        • I got news for you, those stainless steel chain-maille butchers gloves go for $180.00; a wallet isn't going to be less because it'll take about the same amount of chain-maille plus the leather internals,

          Why would you want a chain mail(*) wallet? It doesn't have to flex that way, and the mail won't give you some kind of special resistance to RF. With the right setup of chicken wire, you could probably do the same thing, for about $20.

          (*: Like "breastplate", "chain mail" is a perfectly valid English word.
    • by niceone (992278)

      So this is essentially a giant tinfoil hat for your office? Will it stop the voices as well?

      I don't think it will stop 'the voices' - they are probably your managers

    • by arivanov (12034) on Saturday August 26, 2006 @03:43PM (#15985741) Homepage
      It does not need to be a tin hat.

      Our office has IR tempered glass (which is quite common in "all-glass" buildings nowdays.

      Stops WiFi dead in its tracks. The signal drops by 20+db when going outside the building to the point where you can no longer home in with a normal receiver. Granted, this will not help against a professional attacker, but it is more then enough against random wardriving k1dd10tz.

      So if you have to chose between two buildings which are all-glass and glass windows + wall for a new office the all-glass is better as far as WiFi is concerned. Wardrivers aside, allocating channels without worrying about neighbours is quite a nice thing to have.
      • by Anonymous Coward
        It depends on how close the road is. 30db gain is allowed legally.

        Go past legal and at lot more than 30db can be done.

        20 db drop is only good if you network stays under 20db itself. If you fit a 30db arial inside a 20 db shield you shoot self in foot. A farday setup cannot be broken by just fitting a larger arial. But it can block mobile phones. Both ways have a price.
      • Police where I live complain that their 800 MHz radios cut out in modern office buildings. Firefighters are in the same band. Think twice before you RF-proof your building.
    • Can you hear me now? (Score:4, Informative)

      by Spazmania (174582) on Saturday August 26, 2006 @04:20PM (#15985834) Homepage
      "Can you hear me now?" No, in fact it will stop your cell phone reception too.
      • by megaditto (982598)
        That depends on the design.

        For a quick proof of concept, your microwave oven's FC will 'stop' your cordless phone, but will not stop your cell phone (try it!).

        Even 2" aluminum schielding will not stop some frequencies, e.g. short gamma-rays!
    • The ones on your mobile phone and on the radio?

      Probably :)
    • by jaredcat (223478)
      Will it stop the voices as well?

      Yes.. it will stop all the voices coming to the cell phones of people inside the building.

      Seriously, what kind of crazy idea is this?
  • by jdhutchins (559010) on Saturday August 26, 2006 @02:28PM (#15985499)
    While adding a thin mesh around the building might not be hard to do at construction time, it seems the author has ignored windows. Most larger commercial buildings have large windows, which would need to be covered in a mesh in order to make the whole building a farady cage. This would obviously seriously impact the building's appearance, and I doubt would ever become practical. It's not that difficult to set up a WPA2 or VPN setup if you're concerned about keeping wifi secure.
    • by mrraven (129238)
      Actually if you read the fine(?) article he does mention windows.
    • by zlogic (892404) on Saturday August 26, 2006 @02:43PM (#15985560) Homepage
      I totally agree with you. Until Windows is replaced with something more secure, the network can be easily accessible from outside.
      Oh wait...
      • by cgenman (325138)
        Or someone can start giving USB [csoonline.com] drives to your employees, pose as a remote contractor over the phone and get a password, target a custom AIM virus/trojan, use a telescope through an open window, etc.

        If you can't secure a wireless network to the point where there are much bigger security issues than someone attempting to wardrive it, you shouldn't be defining a company's construction plans.

    • by Brett Buck (811747) on Saturday August 26, 2006 @02:47PM (#15985573)
      Window shielding is a well-established technology. Note http://www.lessemf.com/plastic.html [lessemf.com]. This has been done for decades for secure facilities. There's nothing new about RF shielded/Faraday cage buildings.

                  Brett
    • by ScrewMaster (602015) on Saturday August 26, 2006 @02:54PM (#15985595)
      ... which would need to be covered in a mesh in order to make the whole building a farady cage.

      Not necessarily. I would imagine that some kind of transparent conductive coating could be sprayed onto the glass, and reapplied periodically. For example, my car's windshield has a conductive layer that is used as the radio antenna (it also inconveniently blocks my tollway transponder, something I did not foresee when I ordered the thing.) I'm sure that there would be plenty of window manufacturers that would be happy to sandwich a clear conductive layer in their products were there a demand for this.

      Yeah, you're right it's not that hard to provide a decently secure wireless setup ... but a whole heck of a lot of businesses don't seem to have a clue how to do it. And even if they have an efficient IT department, there's always the idiot that jacks a WRT54G into his office Ethernet port and sticks it under his desk. A giant Faraday cage would provide at least some protection against external snooping and user stupidity. There was an article posted here on Slashdot a while ago about a couple of guys that built a shotgun antenna and went couch-fishing for bluetooth signals in office buildings. They picked up a whole lot of things that they shouldn't have been able to.
      • It seems like it should be trivial to apply a thin, transparent film to windows to block RF signals, something like the RF equivalent of those privacy films you can get for bathroom windows so your neighbors can't watch you in the shower (not that they'd want to see most of us in the shower anyway...) A thin wire mesh implanted into a transparent stick-on plastic film you could put on the inside or outside of your windows.

        Heck, there's probably already such a product out there, I'm just too lazy to actually
        • Re: (Score:1, Troll)

          by ScrewMaster (602015)
          I can't (and don't want to) imagine what the average Slashdotter looks like in the shower. But another poster linked to an outfit that sells just the sort of thing you're talking about.
        • No it's not trivial, infact it can be a real bitch to get the film to stick to the glass without bubble or wrinkels the first few times you do it. The films do come in conductive types like half aluminized to make one-way mirrors, or gold for heat reflectice. Never checked a roll with an ohm meter so I don't know if it's 100's of megohms or a couple of kOhms so it's hard to guess what the shielding efficencies would be.
    • Most windows (for residential construction, anyhow) already have an insect screen. These days most of these are plastic, but they used to be made from aluminum, which would shield the window quite nicely. And no, they don't look all that bad either.
      • by Anonymous Coward
        Most buildings where you live maybe. Here in the UK we never see them.
    • Look under the EMI link at the left sidebar [armorcoatfilms.com] Provides blast protection and by being partially reflective, visual protection of a kind too.
    • They're called window screens.

      Seriously, blocking can't be to bad if you plan ahead. They already make several flavors of wallboard with various other additions for specialty applications - wire mesh should be worth it - and they do have styro' insulation with metal foil backing.

      I've lived in a older house with plaster walls with wire mesh backing (it was common in the 50s or so) plus window screens did a fairly good job of cutting down wifi.

      At work the rebar concrete and steel framing in some of our build
    • by IdahoEv (195056) on Saturday August 26, 2006 @03:30PM (#15985707) Homepage
      Moreover, if it was done correctly it would completely prevent cell phones and blackberries from working. I doubt that would fly in today's business environment.
      • by DeadChobi (740395) <DeadChobi@NoSpAM.gmail.com> on Saturday August 26, 2006 @03:53PM (#15985760)
        Not to point out the obvious or anything, but it's also possible to set up an antenna on the inside which will repeat a signal to an antenna on the outside of a building. They do this in sports stadiums and various other places because of the lack of reception. The antenna doesn't repeat all frequencies, meaning that you can set it to repeat your crackberry's signal but not your ultra-secure Wifi signal.
      • by twostar (675002)
        Depends on the environment. I know many companies have areas that cell phones are not allowed within. Come to think of it, they're already enclosed in faraday cages. A lot of top secret sites do this as a minimum level of control.
    • by kimvette (919543)
      Actually, if windows using a mesh like microwave ovens do, the mesh can be powder coated and resemble tint from a distance, and would appear to be a screen only upon close inspection. You've seen opaque decals on automotive windows, right? There are small circular holes to allow for visibility, but a good amount of glare and IR are blocked from entering the interior, and yet those decal films conform with many strict local laws regarding tint.

      If, for example, a perforated aluminum film is applied, it can be
    • by TA (14109)
      >While adding a thin mesh around the building might not be hard to do at >construction time, it seems the author has ignored windows. Most larger >commercial buildings have large windows, which would need to be covered >in a mesh in order to make the whole building a farady cage.
      [..]
      >,and I doubt would ever become practical.

      I regularly visit a customer which owns a building constructed as
      a faraday cage. It has large windows (3 meters tall) which looks
      normal to me, but the whole building seems
  • UK defense system (Score:5, Interesting)

    by legoburner (702695) on Saturday August 26, 2006 @02:29PM (#15985501) Homepage Journal
    BAE in the UK [silicon.com] have made a wallpaper to do just this. No word on if it is available to consumers though I bet there is a market in the paranoid EM fearing folk that live near 'evil' cell phone masts.
    • Re:UK defense system (Score:4, Interesting)

      by macemoneta (154740) on Saturday August 26, 2006 @04:18PM (#15985828) Homepage
      My parents established an RF shield on our home back in the 1960s. Of course, back then it was called foil and flock wallpaper and it was quite hideous. It still was an effective RF shield. It also made a dandy electrical conductor as I found out, when a foil edge made contact to the hot in an outlet. Something to keep in mind as you RF shield your buildings.
  • by jmauro (32523) on Saturday August 26, 2006 @02:30PM (#15985503)
    Only if you don't want cell phone coverage or look out side. I work in a building that is EM sheilded using a Faraday cage. It was designed to test new radios so you didn't want outside signals coming in to mess up the test. Needless to say a all-metal no windowless office sucks. You have to go out side to make a cell call and when the AC breaks you're screwed because the place turns into an oven with no windows to open. It's a nice idea, but I doubt most wouldn't like to work in such a place 24-7. I sure don't.
    • Re: (Score:3, Insightful)

      by Cthefuture (665326)
      A Faraday cage does not require a solid sheet of metal. It can be a wire mesh.

      There is stopping you from having windows. All you need is a metal screen either on the inside or outside. This also allows you to open the windows for some air. There is also EM blocking glass that has a very thin mesh overlaid or embedded which is basically invisible (similar to some touch screens).

      The only times I have been in EM protected areas with no windows is when there was confidential work being done and they didn't
      • So if it block EM, how does light get in?
        • by JesseL (107722) on Saturday August 26, 2006 @03:44PM (#15985742) Homepage Journal
          A wire screen tends to block EM with a wavlength greater than about twice the size of the holes in the mesh. Since the visible spectrum is in the few hundred nanometer range, and most RF communication happens at wavelengths over 5 centimeters, a screen is a very viable option.
          • Re: (Score:3, Interesting)

            by budgenator (254554)
            The missile I worked on had thin gold wires embeded into the parabolic reflector at 1/4 wavelength intervals so that it would only reflect the frequency we used, as an anti-jamming measure. They could block a WIFI frequency and very little else, I suspect a 2.4GHz cordless phone wouldn't penetrate, but a cell phone in the 900MHz range might not be affected at all.
        • Re: (Score:2, Informative)

          by Mr Z (6791)

          It's all about the wavelengths. If you want to block ALL EM, then yeah, you need a solid metal enclosure. But, just like you can see into your microwave oven through a wire mesh, you could also put windows on your faraday cage as long as they were covered by an appropriate wire mesh.

          IIRC, the 2.5GHz of a microwave oven beam and the 2.4GHz of WiFi are both around 12 cm wavelength. The holes in the mesh on your microwave are so small that the microwaves can't make it through it without severe attenuat

    • Re: (Score:2, Insightful)

      by mad_minstrel (943049)
      Most wouldn't want to work 24/7 anywhere at all.
    • Why would you want Windows? Linux is far better.
    • by Eivind (15695)
      You're assuming there are no transparent yet conductive films. This assumption is false.

      You are assuming that a wall/roof/floot that incorporates a thin layer of something conductive (say aluminium-foil) needs to look like a "metal wall", this is in no way true. Where I live building-regulations already require a plastic vapor-block in all outside walls, these are *inside* the walls (on the "warm" side of the insulation) and not even visible. I fail to see how it'd make the building less nice to be in if

  • Leaky (Score:5, Interesting)

    by QuantumFTL (197300) * <`moc.liamg' `ta' `kciw.nitsuj'> on Saturday August 26, 2006 @02:30PM (#15985504)
    I'm sure this will help minimize effects of leakage, but no building can have a "perfect" faraday cage on standard wifi frequencies - the wavelengths are far smaller than the openings required for humans to enter and exit the building.

    Once again, it's probably better to focus on good encryption, though this is hardly much help to defeat certain on-site DOS attacks. Then again, that's what your security force is for :)
    • by Noishe (829350)
      I suppose then it's also impossible to prevent air from entering and leaving an enclosure with people in it because the air can fit through all the holes that people fit through to enter.... Oh wait... Air Locks...... Hmmmm, maybe a double door entry system to a building would work?
      • Air Locks...... Hmmmm, maybe a double door entry system to a building would work?

        That's actually a very good idea (I can honestly say I had not thought of that), however you'd also have to faraday cage all of the windows, floors, and cielings as well. Outside the building, (if you own the property) a bunch of other wireless access points sending random info etc might provide some good "jamming", or perhaps even as a honeynet.
    • by DeadCatX2 (950953)
      MRIs use very sensitive head coils to pick up their signals. The room that the bore is in needs to be enclosed in a pretty good Faraday cage to prevent EMI from messing with the receiver.

      Granted, windows aren't a problem in the magnet room, but the doors are. So it becomes interesting to try and develop a door that can seal out the frequencies of interest effectively. It's tough, but some magnet rooms can effectively seal off noise while allowing humans to enter and leave.
    • Re:Leaky (Score:4, Insightful)

      by ip_vjl (410654) on Saturday August 26, 2006 @03:44PM (#15985743) Homepage
      Visible light is just another part of the electromagnetic spectrum, but you can easily create a human doorway to another room that keeps light out, even when in use.

      The two types I've seen in photo darkrooms are:
      1) The light baffle. The entry doorway is just an 'S-shaped' hallway that requires you to turn a couple of times to pass through. There doesn't need to be any door to open/close, but as long as it isn't lined with a material reflective to what you are trying to keep out, you're ok. Look under your sink at the drain catch for the idea. The nice thing about this style door (for darkrooms, etc) is that you never need to worry about having to mess with any door mechanism in the dark. It's completely open to wander in and out (for people, air circulation, etc.)

      2) The revolving door. There is never an open conduit from the outside to the inside at any time. The opening closes off from the external environment completely before reaching the point where it opens to the internal environment.

    • by Eivind (15695)
      It's useless (or nearly so) as a security-measure.

      It migth still help reduce interference from the enormous number of wireless devices existing in some downtown neighbourhoods.

  • Cell Phones (Score:5, Insightful)

    by Soul-Burn666 (574119) on Saturday August 26, 2006 @02:30PM (#15985508) Journal
    After succeeding in preventing the wi-fi signal from "leaking", you are surprised your cellphone stopped working.
    • by Daxster (854610)
      ..Although it's easy enough to set up GSM/cell phone repeaters, is it not? I worked in a remote construction site which had a local (analog..) cell antenna for cell phone usage. I do not know how it worked, but the nearest tower was out of range for phones.
      • by tilde.d (994884)
        You would most likely need at lest 3 repeaters: GSM, iDEN, and CDMA. That's just for cell phones, one for each major technology (I don't know what Virgin Mobile uses, probably one of the above; doesn't take into account actual satellite phones).
        • by Daxster (854610)
          That sounds about right, as there were a few cellphone-looking antennas sticking out of the modular office buildings near where the "hotspot" was. There were all sorts of dishes on top of the buildings, which looked a lot like line-of-sight wifi connections.
  • Oh, come on (Score:5, Insightful)

    by happyemoticon (543015) on Saturday August 26, 2006 @02:33PM (#15985522) Homepage

    The best wireless security solution is just to not use wireless. Yes, it's sexy. Yes, I know it can be a pain when there's a split in an ethernet cable that's in the rafters. Yes, I like to be able to use this laptop on the couch because it helps my creative energies get flowing. But seriously, if I were at all concerned about security, I'd just stick at CAT5E into the side and be done with it. Big wireless deployments are things for college students and people who like cafes. If I were running a business, I wouldn't throw money at a wireless project to begin with, let alone build an elaborate jamming/shielding system to correct problems which could've been avoided by not doing anything in the first place.

    • by Yold (473518)
      It isn't always practical to "just not use wireless". Sometimes (always) corporate managers who are more concerned with profit than security are calling the shots, and aren't really concerned with some uber-hacker infiltrating the wireless network. Don't get me wrong, we take security very seriously because it is regulated by federal law (HIPAA), but the damage of a security breach is greatly outweighed by total $$$ savings.

      For example, WiFi has saved the hospital I work at tens of thousands (at least). C
      • by no_pets (881013)
        In this case shielding wouldn't work anyway. If someone wanted to hack the network they would just hang out in the waiting area with a laptop.
    • Yes, just like the best Internet security solution is to never connect the computer to anything. No wait, in fact, don't even turn on the computer--don't even touch it. Then I promise, you'll never have any problems.
    • The best wireless security solution is just to not use wireless.

      You know, we have this stuff called "cryptography"... it has been used to secure communications for quite a while now sucessfully to secure some pretty important things. In fact, I bet you use it directly or indirectly on a daily basis. I have some interesting news: you can use this magical crypto stuff to secure your own wireless communications too! No, seriously! Believe it or not, people actually can and do run secure wireless networks out t

  • by Anonymous Coward on Saturday August 26, 2006 @02:34PM (#15985530)
    So we can replace the wires from each user to a building-wide mesh of wires.
  • Sheet rock (Score:2, Interesting)

    by diablovision (83618)
    The cheapest way to do this would probably be to embed a mesh into the sheet rock. The manufacturer of the sheet rock could do this in their factory; you'd just select the "faraday sheet rock" model when remodelling. No extra labor costs, which, after all, is the biggest part of construction.

    Still probably going to be rather expensive, it being a whole "chicken and egg" type of situation.

    It's probably cheaper on the whole to use good wireless security and regularly test for employees opening unsecured wirel
    • by jhines (82154)
      "Still probably going to be rather expensive, it being a whole "chicken and egg" type of situation."

      Expensive yes, but available. Lead lined sheetrock is available for doctors offices and other places that use X-rays.
    • just tack some good old chicken wire to the studs before you put up the drywall, bond it to the conduit if your really paranoid.
    • The cheapest way to do this would probably be to embed a mesh into the sheet rock. The manufacturer of the sheet rock could do this in their factory; you'd just select the "faraday sheet rock" model when remodelling. No extra labor costs, which, after all, is the biggest part of construction.

      Utterly, completely, and laughably incorrect.

      In order to form a Faraday cage - all the edges of the all the mesh in all of the sheetrock have to be connected together (very expensive in terms of labor) without

    • reinforced cement sheetrock is actually quite common.
  • by azrider (918631) on Saturday August 26, 2006 @02:43PM (#15985559)
    A long time ago, I was a contractor for an establishment whose headquarters was over 4 city blocks and >10 stories above. The building was constructed entirely as a Faraday Cage (nothing inside got outside, checked on a regular basis). When the building was first constructed, the contractor adhered the wire mesh (windows were already shielded) with standard galvanized nails (inside receptor/conductor through shielding/outside transmitter). Go figure...
  • by Animats (122034) on Saturday August 26, 2006 @02:53PM (#15985593) Homepage

    Real Faraday cages are an unmitigated pain to deal with. The ones used for RF testing typically have a heavy door, like a walk-in refrigerator, with conductive fingers all around the doorframe that seal against the door. It's not enough to have metal; all the metal has to be connected. And slots will pass a wavelength up to the length of the slot.

    The ones used for high-security classified work are even worse. They're made of welded metal panels. They're a few feet off the ground, so the underside can be checked. Any I/O is fibre optic. Power goes in through huge low-pass filters. Air goes through metal mesh filters. Double doors work like an airlock, and there's a compressed-air system to force the RF-tight door seals. Periodic testing (transmitter inside, receiver outside) insures the tank is really RF-tight.

    Not a fun work environment.

    Painting the walls with conductive paint is a joke.

    There's nothing mysterious about any of this. RF propagation is well understood, and the test gear is easy to obtain. Ask any ham.

  • In my research lab, we have a Faraday caged room with dimensions of about 35feet x 50feet x 30feet. We house 3 NMR spectrometers there, and use the cage to shield us from stray RF from radio stations and other sources. (The lab is in NYC, and as you can imagine, there's a lot of EM noise).

    The system works quite well, but we still get quite a bit of leakage through the two doorways (they have a copper lining as well). We can still pickup cell phone calls within 3-4 feet of the doorway (when closed), but
  • Hmm, I'm in need of a new wallet... where can I get one of these $15 anti-RFID models?
  • by gsn (989808) on Saturday August 26, 2006 @03:06PM (#15985635)
    There shouldn't be a problem if you had unshielded windows as long as long as we are not talking about a building with all glass on one side. The Faraday cage wil shield pretty effectively even if there are some gaps. This is why you can get away with using a mesh rather than putting everything inside solid metal boxes. If you've even seen the lightning demos with people in cages being completely unaffected while a big Van de Graff shoots sparks around the place (MOS in Boston has this - its fun).

    This seems like its overkill - be more sensible to have some encryption and maybe a system where you have to login to get access to the web is more practical. This way you get to keep what few bars you have on the cell.

    With respect to the RFID in passports or on cards, yeah you might want a Faraday cage in your wallet but I wonder how long it is before that becomes classified as suspicious behaviour. I can just see those TSA officials getting red in the face that you'd dare question their authority by using a shielded wallet and having you detained for an hour - just enough to miss your flight.
    • by N3Roaster (888781)
      With respect to RFID in passports, the Faraday cage (at least for US passports) supposedly will be built into the passport (old news) so the signal only leaks out when the passport is open. No doubt the government is just waiting for the right time to take that out of the plan when nobody is looking (as long as this is a tinfoil hat article). After all, my non-RFID passport is already machine readable.
  • Well, at 2.1 GHz [moonblinkwifi.com] (which is the low end of wireless), the wavelength is 14 cm [sengpielaudio.com]. So you need to keep the largest orifice in the cage smaller than that, and in reality probably much smaller. A general rule of thumb that I've heard for real good EMI containment is something like 1/12 of the wavelength. OK, so somewhere between about 1 cm and 14 cm.

    Not very practical for a building or even a room, except for a special EMI testing room.

    Or maybe I'm completely missing something. Maybe it doesn't take that m

    • Re: (Score:2, Insightful)

      by jpardey (569633)
      It isn't that hard to stop that kind of thing, actually. Best kind of wire for it: standard ethernet cables. Buy a few switches off of ebay just as everyone else tries going wireless.
      • At a facility I work at, there's so much non-optical cabling that they occassionally have interference from cable cross-talk. Using optical cables, that doesn't happen. Wire transmissions can be detected from outside an unshielded building, even if the cables go thru normal metal conduits.
  • by DoubleRing (908390) on Saturday August 26, 2006 @03:13PM (#15985660)
    There are so many ways of securing a wireless network without the messy business of placing a mesh wire around the building. The university in the town I live in has a campus wide wireless network. They then use a vpn system (cisco, I believe) to regulate access. Simply, anyone can connect to the wireless network, but you are given no access unless you connect to the university's vpn. Then from there, depending on that account's permissions, you can access the Internet and the university network permissions. I think this system is probably the best ideas because very little additional hardware is required, each account has a separate username/password combination (if the password is compromised, you only are dealing with a single user), and has the added bonus of being able to access the university resources from home. Plus, it works flawlessly with Linux.
    • by Knetzar (698216)
      At my school, you couldn't get a public ip address without registering your mac address with your school account. Once the network card is registered, then you no longer need to log onto the network.
  • ....wouldn't it just be easier to use a wire rather than construct a building in such a manner? Or use a powerline network instead? Nobody worth their tin-foil hat would ever think such a drastic measure was worthwhile.
  • by B5_geek (638928) on Saturday August 26, 2006 @03:25PM (#15985696)
    This is incredible, all this time I thought I just had bad luck. I can't get 1 bar of signal strength on my cell phone, unless I prop the phone against my window and point it at the cell phone tower that I can see ~500' away.

    And WiFi? No way! I have 3 access points (One in attic, one in basement, one on the same floor as the PC using it (10' away on the other side of a wall) and do you think I can get a reliable signal? Hell no, but if I am in my car I can pick it up 2 blocks away.

    My wifes old 900MHz phone works fine, my new 5.8GHz phone? it'll only work if I stay in the same room as the base-station and the people can only hear me when I yell.

    If I try using 802.11a, I get good results (despite my wifes phone and 2 microwave ovens in the house), my CRAP (Completly Ridiculous Assinine Pet) theory is that the lower frequency passes through the super-human drywall that my house is made of. But to compete with that theory I can't understand why a Nerf-ball is able to dent the wall.

    Time to move I guess.

  • by xkr (786629)
    Didn't I see the Cone of Silence on TV? A while back?
  • (a) static configuration: no arp, no dhcp.
    (b) declare an ipsec tunnel from your laptop to your gateway.
    (c) set ipsec policy to require it for all traffic.
    (d) rtfm

    ip link set dev wireless arp off up
    ip address add dev wireless local 192.168.1.2 peer 192.168.1.3
    ip neighbor add dev wireless to 192.168.1.3 lladdr 00:11:24:2c:38:c6 nud permanent

    setkey -c >/dev/null <<-END
  • It'll only take one carpeter, plumber, electrician, etc. to knock a hole in a wall, install a new door or replace a window without specing the proper RF blocking capability and the original Faraday cage will be rendered useless.

    No doubt, there are some sensitive defense department or NSA facilities that already have RF blocking capability. But maintaining it probably requires careful attention to anything that might compromise it, including periodic testing. In other words, high expense.

    The sort of people t

  • If you're that concerned about security, and are willing to build a faraday cage into your building, why not just run ethernet and use that? It can't "leak".
  • by Randseed (132501) on Saturday August 26, 2006 @04:55PM (#15985938)
    A certain major medical center in the United States which was built in the late 1960s acts as a Faraday cage "by accident," much to the supreme annoyance of everyone involved. Basically, for whatever reason, when they built the building, they used some chicken-wire-like material that's at just the right dimensions to block 2.4GHz wireless transmissions. They didn't do it consistently, either, because they never thought of this. As a result, there are places where cell phones are Faraday-caged-out, places where WiFi works through an internal wall next to places where it doesn't, and so on. It's such a huge pain in the ass that they've had to put about three times the wireless access points that they otherwise would need to, and they still have dead places.

    So yes, it does work.

    • Re: (Score:2, Funny)

      by Shadyman (939863)
      That's similar to the metal rebar in office buildings that hinders (absorbs or reflects) cell phone signals.

      Can you hear me now? No? Good.
  • A Faraday cage needs a metal mesh around the space you want to isolate, with the meshes at most of the size of the wavelength you want to stop AND it needs to be GROUNDED. Otherwise all it does is dampen the signal (the metal mesh absorbs it, then radiates it again like an antenna). So that precludes things like 'Faraday wallets' and... tinfoil hats (unless you attach a metal chain to it and drag it on the ground...)
  • did i miss something, or wasn't WPA or WPA2 'secure enough'? i know it's relatively easy to hack wep, but AFAIK, WPA with a good password hasn't been hacked yet? so why do stories about how to block wifi signals at significant cost always pop up now and then?
  • Now we really know why they put in that wire mesh "fire-rated" glass... Maybe that's the origin of the "firewall" as well. ;-)
  • OMG (Score:3, Funny)

    by Blakey Rat (99501) on Saturday August 26, 2006 @07:40PM (#15986510)
    So now the attacker has to come into your foyer and sit around instead of being able to do it from the coffeeshop across the street!

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