fulldecent/system-bus-radio is a C project with 6.7k stars in the Security space. Transmits AM radio on computers without radio transmitting hardware.
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This program transmits radio on computers / phones without radio transmitting hardware.
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Why?
Some computers are intentionally disconnected from the rest of the world. This includes having their internet, wireless, bluetooth, USB, external file storage and audio capabilities removed. This is called "air gapping". Even in such a situation, this program can transmit radio.
Publicly available documents already discuss exfiltration from secured systems using various electromagnetic radiations. This is documented in the TEMPEST guidelines published by the US National Security Agency and the US Department of Defense. This project simply adds to that discussion.
How to use it
NEW: Try it in your browser, click here: http://fulldecent.github.io/system-bus-radio/
Enter the implementations folder, select any of them and compile using make.
make
Run this using a 2015 model MacBook Air. Then use a Sony STR-K670P radio receiver with the included antenna and tune it to 1580 kHz on AM.
Run it and reference the a tune file or make your own!
./main ../../tunes/mary_had_a_little_lamb.tune
You should hear the "Mary Had a Little Lamb" tune playing repeatedly. Other equipment and tuning may work as well. On the equipment above, the author has achieved clear transmission over two meters of open air or one meter through drywall. Different results will be achievable with different equipment.
Are you using an antenna? At the beginning, the author placed the antenna directly on top of the number 4 key and that worked best (on any AM frequency). It was a round antenna. Then once they knew it worked they moved the antenna back. Moving it back reduced the number of frequencies that it worked on, and eventually only that one (1580 kHz) worked. Different hardware will certainly have different frequency response. Here are some results that have been sent in by readers. Please mail [email protected] with your results (including makes and models of all equipment involved) or edit this file directly and create a pull request.
WANTED: Please post your test results using Raspberry Pi and other embedded systems. This may be particularly good targets because of less shielding/hardening of their hardware.
NEW: See our [basic RTL SDR guide] to receive system bus signals using another computer with RTL SDR hardware.
Technical explanation
This program runs instructions on the computer that cause electromagnetic radiation. The emissions are of a broad frequency range. To be accepted by the radio, those frequencies must:
Be emitted by the computer processor and other subsystems
Escape the computer shielding
Pass through the air or other obstructions
Be accepted by the antenna
Be selected by the receiver
By trial and error, the above frequency was found to be ideal for that equipment.
The actual emissions are caused by the _mm_stream_si128 instruction that writes through to a memory address. Inspiration for using this instruction was provided in:
Guri, M., Kachlon, A., Hasson, O., Kedma, G., Mirsky, Y. and Elovici, Y., 2015. GSMem: data exfiltration from air-gapped computers over GSM frequencies. In 24th USENIX Security Symposium (USENIX Security 15) (pp. 849-864).
https://www.usenix.org/node/190937
Please note that replacing _mm_stream_si128 with a simple x++; will work too. The author's experience has been that _mm_stream_si128 produces a stronger signal. There may be other ideas that work even better, and it would be nice to improve this method to be more portable (not require SSE extensions).
The program uses square wave modulation, which is depicted below:
How active is development on fulldecent/system-bus-radio?
The most recent commit recorded on fulldecent/system-bus-radio was 7 months ago, based on the GitHub push timestamp. The repository has 406 forks — one of the better signals of community interest.
How many stars does fulldecent/system-bus-radio have?
fulldecent/system-bus-radio has 6.7k GitHub stars — refresh the page for the live number, or check github.com/fulldecent/system-bus-radio. TopGit mirrors GitHub's count but does not claim minute-by-minute accuracy.
What else is in the Security space?
fulldecent/system-bus-radio is tracked by TopGit under the Security category, alongside 15 GitHub-tagged topics. Trending and Topics pages list peer repositories of comparable stars and language.
What language is fulldecent/system-bus-radio written in?
fulldecent/system-bus-radio is written primarily in C. GitHub's language field is based on the largest share of bytes in the default branch.
What topics is fulldecent/system-bus-radio associated with?
Where do I read more about fulldecent/system-bus-radio?
This TopGit page is a snapshot — the READ ME tab shows the project's own README content (links stripped, images preserved). The GitHub repository at github.com/fulldecent/system-bus-radio is the definitive source.
Why is fulldecent/system-bus-radio categorized under Security?
TopGit places fulldecent/system-bus-radio in the Security category based on its GitHub topics and description (tagged: "airgap", "communication", "communication-protocol"). Categories are assigned from real repository metadata, not editorial guesswork.
Read full README in the tab above.
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