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Can Faraday Cages Tame Wi-Fi?

Zonk posted more than 8 years ago | 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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The truth may be out there... (5, Funny)

Cygfrydd (957180) | more than 8 years ago | (#15985495)

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

Re:The truth may be out there... (1)

mrraven (129238) | more than 8 years ago | (#15985502)

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:The truth may be out there... (3, Funny)

tocs (866673) | more than 8 years ago | (#15985510)

I think the idea is to keep the voices from leaking out.

Re:The truth may be out there... (4, Informative)

Dachannien (617929) | more than 8 years ago | (#15985603)

Will it stop the voices as well?

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

Re:The truth may be out there... (3, Funny)

shmlco (594907) | more than 8 years ago | (#15985673)

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...."

Re:The truth may be out there... (1)

budgenator (254554) | more than 8 years ago | (#15985844)

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

Re:The truth may be out there... (1)

Planesdragon (210349) | more than 8 years ago | (#15985866)

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. It's not like, oh, "gorget" )

Re:The truth may be out there... (1)

niceone (992278) | more than 8 years ago | (#15985706)

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

Re:The truth may be out there... (5, Interesting)

arivanov (12034) | more than 8 years ago | (#15985741)

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.

SCIF (0)

Anonymous Coward | more than 8 years ago | (#15985792)

They have been doing this in the government forever. Look up SCIF or Tempest on google and you'll get a lot of answers.

Can you hear me now? (3, Informative)

Spazmania (174582) | more than 8 years ago | (#15985834)

"Can you hear me now?" No, in fact it will stop your cell phone reception too.

What about windows? (4, Insightful)

jdhutchins (559010) | more than 8 years ago | (#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.

Re:What about windows? (1)

mrraven (129238) | more than 8 years ago | (#15985513)

Actually if you read the fine(?) article he does mention windows.

Re:What about windows? (5, Funny)

zlogic (892404) | more than 8 years ago | (#15985560)

I totally agree with you. Until Windows is replaced with something more secure, the network can be easily accessible from outside.
Oh wait...

Re:What about windows? (4, Informative)

Brett Buck (811747) | more than 8 years ago | (#15985573)

Window shielding is a well-established technology. Note [] . This has been done for decades for secure facilities. There's nothing new about RF shielded/Faraday cage buildings.


Re:What about windows? (3, Interesting)

ScrewMaster (602015) | more than 8 years ago | (#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.

Re:What about windows? (1)

Tremor (APi) (678603) | more than 8 years ago | (#15985637)

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 look for it.

Re:What about windows? (0, Troll)

ScrewMaster (602015) | more than 8 years ago | (#15985732)

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.

Re:What about windows? (1)

budgenator (254554) | more than 8 years ago | (#15985871)

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.

Insect nets (1)

Chemisor (97276) | more than 8 years ago | (#15985632)

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.

Re:Insect nets (1)

Anonymous Coward | more than 8 years ago | (#15985686)

Most buildings where you live maybe. Here in the UK we never see them.

Window problem already solved (1)

new500 (128819) | more than 8 years ago | (#15985675)

Look under the EMI link at the left sidebar [] Provides blast protection and by being partially reflective, visual protection of a kind too.

Re:What about windows? (0)

Anonymous Coward | more than 8 years ago | (#15985680)

I'm no physicist, but wouldn't the lead content in windows be a pretty good barrier to start?

We have this in New England. (1)

jpellino (202698) | more than 8 years ago | (#15985684)

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 buildings does a darn good job of attenuating the signals.

Re:What about windows? (3, Insightful)

IdahoEv (195056) | more than 8 years ago | (#15985707)

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.

Re:What about windows? (4, Insightful)

DeadChobi (740395) | more than 8 years ago | (#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.

Re:What about windows? (0)

Anonymous Coward | more than 8 years ago | (#15985870)

So it's like a firewall for your tinfoil hat? Sweet, I need to get me one of those.

Re:What about windows? (1)

KnightMB (823876) | more than 8 years ago | (#15985843)

The thing about the Wallet though will not work, to block signals you have to have something to ground to and a wallet is basically a floating circuit with no ground, thus will not block signals at all or as well if it were grounded.

UK defense system (5, Interesting)

legoburner (702695) | more than 8 years ago | (#15985501)

BAE in the UK [] 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 (3, Interesting)

macemoneta (154740) | more than 8 years ago | (#15985828)

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.

Faraday Cages will work (5, Informative)

jmauro (32523) | more than 8 years ago | (#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:Faraday Cages will work (2, Insightful)

Cthefuture (665326) | more than 8 years ago | (#15985628)

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 want anything visible from the outside.

Re:Faraday Cages will work (1)

Breakfast Pants (323698) | more than 8 years ago | (#15985683)

So if it block EM, how does light get in?

Re:Faraday Cages will work (5, Informative)

JesseL (107722) | more than 8 years ago | (#15985742)

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:Faraday Cages will work (2, Interesting)

budgenator (254554) | more than 8 years ago | (#15985903)

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:Faraday Cages will work (2, Informative)

Mr Z (6791) | more than 8 years ago | (#15985763)

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 attenuation.


Re:Faraday Cages will work (1)

rjdegraaf (712353) | more than 8 years ago | (#15985836)

The mesh have to be really fine gridded, i.e. near the wave length of the used frequency of transmission to block.

At the lab where I am working now, the experimental room is shielded using copper plates (around 1mm thick); but when the door is open, my mobile phone still receives text (sms) messages.

Re:Faraday Cages will work (2, Insightful)

mad_minstrel (943049) | more than 8 years ago | (#15985633)

Most wouldn't want to work 24/7 anywhere at all.

Leaky (5, Interesting)

QuantumFTL (197300) | more than 8 years ago | (#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 :)

Re:Leaky (1)

Noishe (829350) | more than 8 years ago | (#15985629)

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?

Re:Leaky (1)

QuantumFTL (197300) | more than 8 years ago | (#15985687)

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.

MRI (1)

DeadCatX2 (950953) | more than 8 years ago | (#15985630)

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 (3, Insightful)

ip_vjl (410654) | more than 8 years ago | (#15985743)

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.

Cell Phones (4, Insightful)

Soul-Burn666 (574119) | more than 8 years ago | (#15985508)

After succeeding in preventing the wi-fi signal from "leaking", you are surprised your cellphone stopped working.

Re:Cell Phones (1)

Daxster (854610) | more than 8 years ago | (#15985556)

..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.

Re:Cell Phones (1)

tilde.d (994884) | more than 8 years ago | (#15985617)

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).

Re:Cell Phones (1)

jrobinson5 (974354) | more than 8 years ago | (#15985631)

Most companies provide cell phones to employees, presumably they could just get cell phones that all use the same technology.

Re:Cell Phones (1)

tilde.d (994884) | more than 8 years ago | (#15985651)

Your statement is true only if the company needs to constantly be in contact with you (e.g. CEOs, Bosses, roving IT) but if there is no need for constant communication then they won't. For example, if I work in the mail room, why would they want to give me a cell phone. It would be just additional cost. The final solution would be no cell service at work... doable but not a positive morale booster.

Re:Cell Phones (1)

Daxster (854610) | more than 8 years ago | (#15985640)

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.

Re:Cell Phones (1)

ryeinn (844805) | more than 8 years ago | (#15985872)

Personally, I would love to work in a relatively Faraday caged building. Heck, they could even just cage individual rooms. As a high school physics teacher it really gets annoying when the students are so addicted to their cell phones that they check for text messages every five minutes.

I may even think about doing it myself, how much would 1500 square feet of wire mech cost....The whole key is that the mesh around the building/room is continuous at the edges.

Oh, come on (5, Insightful)

happyemoticon (543015) | more than 8 years ago | (#15985522)

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.

Re:Oh, come on (1)

Yold (473518) | more than 8 years ago | (#15985636)

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). Certain doctors now carry tablets and iPaqs, and this has significantly improved productivity. Tablets enable them to access any supplemental patient info that isn't on the patient's chart, rather than waiting for someone to print it off. They can even access information at other facilities, to retrieve things like lab results and MRIs that were down outside our hospitals. IPaqs make their schedule and (more importantly) email readily available, so they don't have to get paged, and then call a secretary to get a msg. Specialists/Surgeons are VERY expensive people, so wasting as little time as possible save the corporation hundreds of thousands every year.

TIME=MONEY, its as simple as that. Wireless can save certain businesses TONS of money, by reducing the "unproductivity" of expensive personnel.

Re:Oh, come on (1)

no_pets (881013) | more than 8 years ago | (#15985665)

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.

Re:Oh, come on (1)

DoubleRing (908390) | more than 8 years ago | (#15985723)

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.

Thank god we got rid of wires (5, Funny)

Anonymous Coward | more than 8 years ago | (#15985530)

So we can replace the wires from each user to a building-wide mesh of wires.

Sheet rock (2, Interesting)

diablovision (83618) | more than 8 years ago | (#15985544)

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 wireless networks using some workstations with wifi cards running shell scripts looking for unsecured networks....

Re:Sheet rock (1)

jhines (82154) | more than 8 years ago | (#15985561)

"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.

Re:Sheet rock (1)

budgenator (254554) | more than 8 years ago | (#15985981)

Lead lined sheetrock I don't think so, I once put up lead, it came in a roll, was 3/32 in. thick and was a heavy bitch to work with. I just cut it with heavy shears, tacked it to the studs and then put a layer of drywall over it to really hold it in place. I'd think that putting the lead in the sheetrock would make it nearly impossible to handle without it snapping or delaminating.

Re:Sheet rock (1)

budgenator (254554) | more than 8 years ago | (#15985951)

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.

Faraday Cage (3, Funny)

azrider (918631) | more than 8 years ago | (#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...

Have you ever actually used a Faraday cage? (4, Informative)

Animats (122034) | more than 8 years ago | (#15985593)

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.

We have a Faraday caged room (2, Interesting)

digitalderbs (718388) | more than 8 years ago | (#15985597)

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 not much more than that. However, the room is quite dead for WiFi transmission.

Solves the wrong problem (0)

random coward (527722) | more than 8 years ago | (#15985623)

A Faraday cage solves the wrong problem.

It will stop external interference from entering the building;
However, it wont stop your signal from leaving though.
So people people can still sniff and listen, but you get very low interfernance
and noise.

Re:Solves the wrong problem (2, Informative)

Bishop (4500) | more than 8 years ago | (#15985667)

A complete faraday cage will contain RF EM waves for the same reason that it will keep EM out.

Re:Solves the wrong problem (1)

The Mighty Buzzard (878441) | more than 8 years ago | (#15985691)

Well, you got the solving the wrong problem bit right. The real problem isn't how to keep the idiots on the outside out, it's what to do with the idiot lusers that management hired.

Re:Solves the wrong problem (0)

Anonymous Coward | more than 8 years ago | (#15986097)

A Faraday cage solves the wrong problem.

It will stop external interference from entering the building;
However, it wont stop your signal from leaving though.

Then I'm sure you'd be willing to remove the useless wire mesh from your microwave door?

Wallet (1)

HoneyBunchesOfGoats (619017) | more than 8 years ago | (#15985626)

Hmm, I'm in need of a new wallet... where can I get one of these $15 anti-RFID models?

Re:Wallet (1)

johnedmiston1956 (969057) | more than 8 years ago | (#15985768)

Googled it... Blessings, John

Re:Wallet (1)

HoneyBunchesOfGoats (619017) | more than 8 years ago | (#15985917)


Re:Wallet (1)

SeaFox (739806) | more than 8 years ago | (#15986003)

Hmm, I'm in need of a new wallet... where can I get one of these $15 anti-RFID models?

Google is your friend. []

Looks like this [] is where you want to go.

shielded windows and wallets (3, Interesting)

gsn (989808) | more than 8 years ago | (#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.

Re:shielded windows and wallets (1)

N3Roaster (888781) | more than 8 years ago | (#15985812)

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.

I doubt it... basic physics (1)

sdo1 (213835) | more than 8 years ago | (#15985644)

Well, at 2.1 GHz [] (which is the low end of wireless), the wavelength is 14 cm [] . 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 much containment to actually stop 2-way communications at those frequencies


Re:I doubt it... basic physics (2, Insightful)

jpardey (569633) | more than 8 years ago | (#15985849)

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.

Go optical.. (1)

JetScootr (319545) | more than 8 years ago | (#15985901)

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.

The answer is yes (0)

Anonymous Coward | more than 8 years ago | (#15985649)

I know some of you say it's impossible, but I work for a cell company in the states. Our buildings where R&D is done are caged off to prevent our subscribers from roaming onto our test RF. It's pretty amazing, but once you leave the building - I mean JUST as you're exiting the front door you completely loose RF coverage. As others have said, though, this is a problem as there is no where for that energy to go and instead it is absorbed by things like your body. This is the only company I've worked for where a number of my coworkers have gotten brain cancer. Many of us don't think it's a coincidence.

As for the wave length being too hard to cage argument. What wave length does your microwave oven put out - whose magnetron emits 600-1200 watts? (hint: look at the FCC sticker on it, it runs on the 2.4ghz ISM band) Does your wifi go to crap everytime you nuke a hotdog? If so, it's time to get a new microwave oven...

Re:The answer is yes (1)

kfg (145172) | more than 8 years ago | (#15985869)

. . .there is no where for that energy to go and instead it is absorbed by things like . . .

The Faraday cage. That's the whole point of the thing. The cage disperses the energy it has absorbed by reradiating it at a different wavelength refered to in the vernacular as "heat."

Sooner or later all this "heat" gets radiated to the outside of the building (which is secure, because by this point it carries no information other than the pure carrier). There is a very, very small amount of this extra "heat" radiation absorbed by the body, but you may find that your building also has ways of evacuating exesses of it to the outside.

In fact, if you object to this "heat" stuff we can actually do something to keep most of it out of your room, but you might find that that too has certain negative effects on health.

On the whole I really wouldn't worry about it unless, . . .you are more massive than your walls.


Re:The answer is yes (1)

budgenator (254554) | more than 8 years ago | (#15986027)

... there is no where for that energy to go and instead it is absorbed by things like your body. This is the only company I've worked for where a number of my coworkers have gotten brain cancer.
Pencils, the graphite in the pencil lead sucks up microwave something fearce. Try it, put one of those golf pencils (without the metal ferrel for the eraser) on top of your coffee cup before you nuc' it in the microwave, and compare the temp to a normaly cup! If the cops weren't using lasers, my car would be painted graphite black!

Idea (0)

Anonymous Coward | more than 8 years ago | (#15985657)

As British researchers found out, stealth bomber skin blocks wifi.

Why does it have to be a physical? (5, Interesting)

DoubleRing (908390) | more than 8 years ago | (#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.

Re:Why does it have to be a physical? (1)

Matthias Himber (982177) | more than 8 years ago | (#15986087)

We have such an system at my uni, too. It's a fscking pain in the ass.
It uses some propietary cisco vpn system that requires a propietary cisco vpn client (a linux version, using a binary-only kernel module, is available)[1]. The software sucks ass. It can keep a vpn connection going for 20 minutes on a good day, but as soon as the wireless connection is less than perfect and starts dropping packets, the vpn connection will fail - *silently*. That's right, the only way to find out that your vpn tunnel is down is when suddenly no data gets through anymore. The client software will continue to cheerfully sit there and say it's still connected. Plus the (propietary cisco) hardware can apparently cope with no more than a handful of users concurrently.
The IT guys refuse to replace the system despite everybody hating it, saying that there just are no alternative systems capable of the same workload. If they are right, then vpn won't solve your problem, unless the number of clients is _really_ small.

[1] A reverse engineered free client exists (vpnc). It doesn't implement all features, but it mostly works. That makes it more reliable than the propietary client, which mostly doesn't work, but it can't fix the flaws in the system.

The USA and RFID passports (0)

Anonymous Coward | more than 8 years ago | (#15985663)

Who'd want such a thing? Quite possibly, you. New UK passports include RFID chips, and future editions of currency might be RFID-enabled too.

The US gov't has already announced they're switching to RFID-enabled passports [] , which supposedly have all kinds of privacy-related issues.

Will Faraday cages around passport-pouches make the RFID chip unreadable?

Ummm..... (1)

kidjan (844535) | more than 8 years ago | (#15985692)

....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.

I must already have this! (3, Funny)

B5_geek (638928) | more than 8 years ago | (#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.

Re:I must already have this! (0)

Anonymous Coward | more than 8 years ago | (#15985785)

Do you live under power lines?

Re:I must already have this! (1)

B5_geek (638928) | more than 8 years ago | (#15985895)

As a matter of fact, I live very close to high-tension power lines.

Get Smart (1)

xkr (786629) | more than 8 years ago | (#15985734)

Didn't I see the Cone of Silence on TV? A while back?

HOWTO: protect your wireless network (2, Informative)

Ivan Matveitch (748164) | more than 8 years ago | (#15985749)

(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 peer
        ip neighbor add dev wireless to lladdr 00:11:24:2c:38:c6 nud permanent

        setkey -c >/dev/null <<-END

                add esp 256 -m tunnel
                        -E aes-cbc 0x25d8d1bbcf9b7b416ebd7ce514627539f12dc64e3e75c5a2 0d13277558056a4c
                        -A hmac-sha1 0x17f98a8f668324191ee406855e81130fb17f7726;

                add esp 512 -m tunnel
                        -E aes-cbc 0x25d8d1bbcf9b7b416ebd7ce514627539f12dc64e3e75c5a2 0d13277558056a4c
                        -A hmac-sha1 0x17f98a8f668324191ee406855e81130fb17f7726;

                spdadd any -P in ipsec

                spdadd any -P out ipsec

Until the remodelers get through with it (1)

PPH (736903) | more than 8 years ago | (#15985761)

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 that want the convenience of WiFi in the office are the same people that insist on lugging their laptop into Starbucks and using the (insecure) WiFi network there. Better to deal with security using a VPN.

Demand a subject then get rubbish. (0)

Anonymous Coward | more than 8 years ago | (#15985782)

Gee ... once I thought that wrapping up your credit card in foil might just be a convincing indicator of mental illness .... I think I'll be adding foil to my shopping list tho .... dang where are my pills.

Wires? (1)

Millenniumman (924859) | more than 8 years ago | (#15985829)

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".

An unintended Faraday shield. (1)

falken0905 (624713) | more than 8 years ago | (#15985884)

I recently setup a wireless ap to give net access to my next door neighbor. I located the ap in a closet on an outside wall facing his house. The distance across the driveway is only about 20 feet but the signal was very low in his house and was pretty much useless. We carried a laptop around outside and found that the signal dropped off very rapidly as we moved away from my house. Out at the street it was virtually gone. At first i was baffled. Then we realized that my house has aluminum siding. Bingo, the ap is inside a giant shield! I relocated the ap to a shelf on a window sill facing his house. Much better, but not as good as expected. I removed the window screen and all is well - he gets good signal anywhere in his house. This arrangement ends up being fairly directional toward his house. Signal strength outside the other three sides of my house is still very low.

Direct experience... (1, Informative)

Anonymous Coward | more than 8 years ago | (#15985885)

My organization had to build a faraday cage for security requirements around a library about 40 foot squarish. It was enormously expensive to put into place in existing construction, what with pipes, cables, ductwork and whatnot to work around.
You must remember - people still have to breathe, so air must go in and out easily and in volume.
I was not directly involved in the installation (I was a user of the library), but IIRC they always had trouble getting it to not leak in some way. Think of RF as high pressure steam - it will always find a leak. Not all RF can be shielded the same way, or the one way that does work is most expensive and hardest.
I'm sure it can be made to work, if designed into the building from the start, but it's very difficult to add later.
WiFi is highly likely to be subjected to a lot of industry brainwork figuring out how to sniff it out thru Faraday cages that are supposedly "secure". I suspect a lotta snake oil could be sold this way.

Inadvertent Faraday Cages (3, Interesting)

Randseed (132501) | more than 8 years ago | (#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:Inadvertent Faraday Cages (2, Funny)

Shadyman (939863) | more than 8 years ago | (#15986247)

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.


m-wielgo (858054) | more than 8 years ago | (#15985958)

Is a set of standards for limiting EMI and RF radiation. We have classified several rooms at work that meet these standards and work very well. Chances are though, unless you're a defense contractor with security clearance, you won't know how to outfit a room to meet the reqs.


CompMD (522020) | more than 8 years ago | (#15986066)

I work with retired employees of a large defense contractor that builds fighter jets. They told me some good stories about TEMPEST work. They were fond of driving around buildings in a van full of radio gear to make sure no RF signals got out of the buildings. Picking up the signals from CRT monitors was entertaining supposedly.

Needs to be GROUNDED (1)

dargaud (518470) | more than 8 years ago | (#15986188)

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...)

why is everybody so concerned about wireless secur (2, Interesting)

schweini (607711) | more than 8 years ago | (#15986217)

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?
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