Slashdot Mirror
Researchers Build Covert Acoustical Mesh Networks In Air
An anonymous reader writes "Researchers at Fraunhofer FKIE, Germany have presented a paper on covert acoustical communications between laptop computers. In their paper 'On Covert Acoustical Mesh Networks in Air', they describe how acoustical communication can be used to secretly bridge air gaps between computers and connect computers and networks that are thought to be completely isolated from each other. By using ad-hoc routing protocols, they are able to build up a complete mesh network of infected computers that leaks data over multiple hops. A multi-hop acoustical keylogger is also presented where keystrokes are forwarded to an attacker over multiple hops between different office rooms. The fundamental part of the communication system is a piece of software that has originally been developed for acoustic underwater communications. The researchers also provide different countermeasures against malicious participation in a covert acoustical network. The limitations of air gaps have been discussed recently in the context of a highly advanced malware, although reports on this so-called badBIOS malware could not yet be confirmed."
They used Lenovo T400 laptops which are circa 2008 models, no extra audio hardware. They could do 20bits/sec over nearly meters 20 meters if they had line-of-site between the laptops.
When information is power, privacy is freedom.
You're both uninformed. Computers don't lack filters. There are analog low pass filters on all audio inputs, because they're necessary (see the Nyquist/Shannon sampling theorem). The thing is, the cutoff frequencies are necessarily above the audible range, because there are no perfect "brick-wall" filters. For systems with sampling rates higher than 44.1kHz, the cutoff frequencies are far above the audible range. Otherwise what would be the point of providing the high sampling rate? Yes, it's audiophile hocus-pocus, but people buy it. None of this is relevant to the topic though, because the researchers used frequencies which are theoretically audible. But most adults don't hear much above 15kHz, so they don't notice these "audible" frequencies. When TVs were still called "tube", did you hear a high pitched sound in TV stores? If not, your audible range is already significantly diminished. The horizontal frequency is ca. 16kHz and the oscillating magnetic field caused parts in some TV sets to vibrate and emit noise at that frequency.