Kim Zetter, Wired:
In the past two years a group of researchers in Israel has become highly adept at stealing data from air-gapped computers—those machines prized by hackers that, for security reasons, are never connected to the internet or connected to other machines that are connected to the internet, making it difficult to extract data from them.
Mordechai Guri, manager of research and development at the Cyber Security Research Center at Ben-Gurion University, and colleagues at the lab, have previously designed three attacks that use various methods for extracting data from air-gapped machines—methods involving radio waves, electromagnetic waves and the GSM network, and even the heat emitted by computers.
Now the lab’s team has found yet another way to undermine air-gapped systems using little more than the sound emitted by the cooling fans inside computers. Although the technique can only be used to steal a limited amount of data, it’s sufficient to siphon encryption keys and lists of usernames and passwords, as well as small amounts of keylogging histories and documents, from more than two dozen feet away. The researchers, who have described the technical details of the attack in a paper (.pdf), have so far been able to siphon encryption keys and passwords at a rate of 15 to 20 bits per minute—more than 1,200 bits per hour—but are working on methods to accelerate the data extraction.
The attacker installs malware on a target machine to modify the fans’ speed to change audio output and transmit information to nearby microphones. Diabolical!