Researchers use sounds from hard disc to steal computer data

Researchers have developed a technique to steal data from a PC by using the mechanical noise coming from the hard disc drives inside.

The hack though not practical, is designed for ''air-gapped'' systems, or computers sectioned off from the internet.

Researchers at Ben-Gurion University of the Negev in Israel had been studying how sound could be used to extract information from air-gapped computers. In  June, they showed that even a PC's cooling fans could be controlled to secretly transmit data, including passwords and encryption keys.

The researchers say in a new paper that a PC's hard disc drive could too produce enough noise to transmit data; they used the drive's internal mechanical arm, to generate binary signals.

The mechanical arm only reads and writes data within the hard drive, but it also creates much sound at varying frequencies, which the researchers decided  to exploit.

They developed a piece of malware called ''DiskFiltration'' that could infect a Linux-based PC to control a hard disc drive's operations. They recorded the emitted noise, on a Samsung Galaxy S4 phone placed nearby, to log and decrypt the signals.

The researchers found that their hack could transmit enough 0s and 1s but the transmission rate was rather slow at 180 bits per minute.

It would take 74 hours to covertly steal a 100KB document at that rate.

However, at that data rate, it would be possible to swipe things like encryption keys or passwords. With diskFiltration, one could get a full 4,096-bit cryptographic key in about 25 minutes.