The first music played on personal computers didn’t come out of fancy audio cards, or even a DAC. the first audio system in a personal computer was simply holding an AM radio up to the case and blinking address pins furiously. This worked wonderfully for homebrew computers where EMC compliance hadn’t even become an afterthought, but the technique still works today. [Chris] is playing music on the radio by sending bits over the system bus without using any wires at all.
[Chris]’ code is based on the earlier work of [fulldecent], and works pretty much the same. To play a sound over the radio, the code simply writes to a location in memory when the waveform should be high, and doesn’t when the waveform is low.
Of course the ability to exfiltrate information over an airgap has a few more nefarious purposes, but [Chris] also has another way of doing just that which is undefeatable by a TEMPEST shielded computer. He can send one bit at a time by opening and closing a CD-ROM drive, capturing these bits with a webcam. Is it useful? It’s hard to imagine how this setup could ever capture any valuable data, but it is a proof of concept.
Electronics leak waves and if you know what you’re doing you can steal people’s data using this phenomenon. How thick is your tinfoil hat? And you sure it’s thick enough? Well, it turns out that there’s a (secret) government standard for all of this: TEMPEST. Yes, all-caps. No, it’s not an acronym. It’s a secret codename, and codenames are more fun WHEN SHOUTED OUT LOUD!
The TEMPEST idea in a nutshell is that electronic devices leak electromagnetic waves when they do things like switch bits from ones to zeros or move electron beams around to make images on CRT screens. If an adversary can remotely listen in to these unintentional broadcasts, they can potentially figure out what’s going on inside your computer. Read on and find out about the history of TEMPEST, modern research, and finally how you can try it out yourself at home!
Continue reading “TEMPEST: a Tin Foil Hat for Your Electronics and Their Secrets”
Researchers from Inverse Path showed a couple interesting techniques for sniffing keystrokes at CanSecWest. For their first experiments they used a laser pointed at the shiny back of a laptop. The keystrokes would cause the laptop to vibrate which they could detect just like they would with any laser listening device. They’ve done it successfully from anywhere between 50 to 100 feet away. They used techniques similar to those in speech recognition to determine what sentences were being typed.
In a different attack, they sniffed characters from a PS/2 keyboard by monitoring the ground line in an outlet 50 feet away. They haven’t yet been able to collect more than just single strokes, but expect to get full words and sentences soon. This leakage via power line is discussed in the 1972 Tempest document we posted about earlier. The team said it wasn’t possible with USB or laptop keyboards.
TEMPEST is the covername used by the NSA and other agencies to talk about emissions from computing machinery that can divulge what the equipment is processing. We’ve covered a few projects in the past that specifically intercept EM radiation. TEMPEST for Eliza can transmit via AM using a CRT monitor, and just last Fall a group showed how to monitor USB keyboards remotely. Through the Freedom of Information Act, an interesting article from 1972 has been released. TEMPEST: A Signal Problem (PDF) covers the early history of how this phenomenon was discovered. Uncovered by Bell Labs in WWII, it affected a piece of encryption gear they were supplying to the military. The plaintext could be read over that air and also by monitoring spikes on the powerlines. Their new, heavily shielded and line filtered version of the device was rejected by the military who simply told commanders to monitor a 100 feet around their post to prevent eavesdropping. It’s an interesting read and also covers acoustic monitoring. This is just the US history of TEMPEST though, but from the anecdotes it sounds like their enemies were not just keeping pace but were also better informed.
Every time you press a key on your keyboard, a small burst of electromagnetic radiation is let out. This radiation can be captured and decoded. Though it only affects some models, this is pretty serious. They tested 11 different keyboards and they were all vulnerable to at least one of the four methods of attack. Tests have shown that the data can be read through walls and up to 65 feet away. That is pretty scary stuff. Someone could be setting up in the apartment or office right next to yours to listen to every keystroke you type. Check out the second video after the break.
Continue reading “Eavesdrop on keyboards wirelessly”