Schneier on Security

A while back The Screensavers on TechTV did a test with this metallic paint. It did cut down the signal, but not to the point were it wasn't radiating from your house.

Further to this, if it cuts down wifi, I'm sure it's cutting out your wireless carriers signal. I'd much rather run ethernet through my house than spend a small fortune on paint reducing my cellular reception.

Todd

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I just wish everyone who writes about this thing says 'Wireless Shielding Paint' instead 'WiFi Shielding Paint' so that readers can straightaway see why it's useless.

Another good test for lead paint...setup a WAP and see if you can get reception as you move around the house.

Wireless signals are like water. They will simply radiate over and around obstacles. Metallic paint might reduce the signal strength, but that's easily compensated for by an antenna.

I have also heard that military agencies can capture and reconstruct TEMPEST signals up to a distance of 1 km with basic equipment. They found this range while routinely testing their own "secure" (e.g. completely enclosed in metal) facilities for radiation leaks. In contrast to a few coats of metallic paint around large windows and doors, the military was looking for TEMPEST leaks as small as a screw hole.

This sort of paint will, indeed, keep cell-phone signals out exactly as well as it will keep 802.11 signals in -- it works for exactly the same reason that you can't get cell reception inside an elevator. I can see some circumstances where this would be useful. Also, it is possible to design wallpaper that will block specific frequency ranges very effectively, but leave others more or less unscathed.

And yes, of course, this won't block all signal -- it won't block signal eminating from windows, doors, and screwholes. What it will do is lower the range from which you can sniff or connect, with constant equipment, which is plenty to be useful for some cases. Consider a building situated near the center of a military base. Up to a quarter-kilometer away is secured area. If you lower the sniffable range of the radiation to within that security perimeter, then you're in a lot better position then if the theoritical sniffers could sniff from an anonymous house in the civilian village nearby.

BTW, re doors, paint the door as well, making sure there's decent electrical contact between the wall and the door (such as over the hinges). Not perfect, but better then nothing.

Personally, I'd have more concerns selling it to the Dept. of Homeland security than to a Middle Eastern government... have you ever looked at our own government, like really? Have you? We're f'ing scary!

In the old building I used to work in (built in the late 1940's), when they were trying to deploy a wireless network they ran into huge problems.

Apparently, they were so concerned about the possibility of them working on something classified in the building and having the communists spy on it, they embedded every wall with a fine steel mesh, which destroyed radio and cell phone signal in the building (cell reception was not exactly a concern in the 40's). It also cut the range of 802.11b to within a 1 room distance... making it practically impossible to achieve the goal of "blanket coverage".

They ended up changing the plan for how to give wireless coverage to the building from "everywhere" to "almost nowhere" and ripping out a few walls worth of mesh in key places to hit priority areas. Yesterday's security choices are today's roadblocks.

Like most RF sheilding products this paint can turn out to be more of a liability than a security aid.

It is posible to arange any conductive medium to actually amplify RF signals in a given direction (think old style TV antena), and in buildings this happens more often than not. For example take a VHF portable radio with a signal strength meter around any modern building and note the strength of your favourite radio station. You are quite likley to find a spot where the signal is considerably stronger inside the building than outside especially at ground floor level.

RF sheilding is very difficult to do properly (ask any one who has set up an RF test laboratory) and for those of you who want to know just how hard search on the internet for TEMPEST and have a read.

Back in June, there was an article on silicon.com that claims that BAE Systems in the UK has developed a stealth wallpaper that essentially does the same thing but allows radio and mobile phone frequencies pass through.

I'm not exactly sure how it works or haven't heard anything else about it since the article came out.

Encryption (e.g. IPSec) is a much better idea.

Well… It seems that people at the DHS are smarter than Middle East civil servants. If you consider the price of the FFW “wallpaper�, you’d better buy 25 yards of aluminium paper at the closest Wall Mart store. It’s far cheaper, and presents approximately the same shielding capabilities… in other words, absolutely none…

Blocking RFI “stray cats� is a tedious task, every ham radio and electronic designer will confirm you this point. To obtain good RF insulation, you have to cover every window, seal the smallest crack, cover every square inch of floor or ceiling… and plug this faraday cage to a good electrical grounding. The higher the working frequency is, the tougher is the job… SHF (signals over 1 GHz) are like water, the smallest hole means leakage.

If you prefer using the “coating� solution sold by the very same company, aka the anti-wireless paint, it is cheaper to buy this black paint used to refresh stoves and old ovens (I’ve seen some at Target). This paint is containing a high percentage of pure carbon powder, and is very efficient in all sorts of shielding at very low cost (I use this kind of paint in hyperfrequency attenuators and anechoïd chambers)

I won’t argue anymore about the “other security gadgets� sold by FFW. The “wifi detector� is useless compared with simple RFI testers (some of them are called “Microwave oven detectors� and are sold everywhere for a few bucks). If you need a more elaborate detection device, you can use public domain or free sniffing softwares installed on PDA’s or portable computers: Kismet, WiFifofum, AirSnort, Wepckrack…
By default, never yield to paranoid advertisements made around the wireless world. Most of them can be classified as “bad� or “useless� security.

BEA commercialize a “WiFi� wallpaper using what technicians call “notch� filters. It is in fact a double side copper/mylar coating engraved with an impressive network of dipoles antennas tuned on peculiar frequencies. This approach is technically efficient, as it blocks only the frequency you wish to control and lets other bands working without problem (for example cell phones or UHF talkies). But the retail price of such a "wallpaper" is very expensive.

At last, I wonder why people would try to block WiFi this way. If you intend to stop any RF radiation from a corporate building, you have to shield the whole place… and multiply the number of Radio Access Point because of the attenuation and unwanted reflexions (bouncing signals) due to the shielding itself. That’s totally unrealistic. If your intend to circumvent RF signals to a very specific room, it could be smarter to use a high end and elaborate technology able to combine security and effectiveness : a 100BaseT copper based cabling system (please, don’t tell others I gave you this info, it’s top secret and brand new)

Sorry for my rotten English… I’ll try to do better next time.

I have read all the comments and I am interested in the possibility of using this Wireless blocking paint for blocking cellular in environments as hospitals, theatres,..ect for all those annoying calls in inappropriate times and places what are a few thoughts on that basic use and/or effectiveness. Any and all comments appreciated.

I am very sensitive to EMF and now find that the signal from my neighbor's wireless router is causing numerous health problems. Please help me - does anyone have a suggestion as to how to block the signal from entering my home??? They could lower the signal strength, but I don't believe they would be sympathetic to my situation. Thanks!

to block the signal , i was told by a commuincations engineer that you would have to encase you house with wire mesh and attach lots of grounding rods going at least 4 foot into the ground . Though i don't see how it would work

Dear Bruce Schneier,

I would appreciate it a lot if you would sell a fully RF shielded box on your website with the back of it providing shielding of the power and video cables in a hollow tube. While on the front of the box it has RF-shielded glass, so that you can just go out and buy whatever type of LCD monitor that you may want. Simply stick it in this box and have a Tempest-equivalent sort of home-brew secure display. This would be like a box that you just stick the monitor inside and there would be shielding also for the cables (much longer than needed) of a flexible material and the entire box would be RF secure. -- a Faraday cage just for your monitor :)

Seriously Mr. Schneier, I would buy this from you. There are plenty of EM shielding companies, but none that offer a simple monitor box that is affordable, that you can stick a monitor inside to make it secure from radiating spurious emissions (TEMPEST leaks).

... And if a glass front that is see-through while also being RF-shielded is not available then you could simply paint the inside of regular glass with an RF shielding paint that is clear. Please *PLEASE* consider my suggestion. If you build it I will buy (and many others as well).

Kind Regards,
Anonymous

I too cannot take the abundance of wireless signals in my neighborhood. My life is definitely affected with insomnia, and headaches and an incessant buzzing. Neurologist checked me out and gave me a clean bill of health. We are irradiating ourselves. The human race is idiotic.

I shouldn't have said what I did about the human race. I am angry. However, there are well documented cases and studies of ill health effects from the pulsed microwave frequencies of wireless along with other frequencies along the magnetic spectrum. Some of us are getting ill, others are not as aware. Go to bioinitiative.org/report for in depth look.