Researchers have discovered that even the sounds coming from a hard disk drive can be used to hack computers.

Remotely accessing data is possible because most systems are connected now through the internet. To counter this, those looking to keep their computers from being hacked are disconnecting from all networks, creating an "air-gapped" system with high security. However, researchers from the Ben-Gurion University of the Negev have shown that even air-gapping is not completely safe.

According to Mordechai Guri and colleagues, a workaround they dubbed DiskFiltration can be used to tap into a computer's hard disk drive and reveal important bits of data. Specifically, DiskFiltration is a piece of malware that be used to infect Linux-based systems and control a hard disk drive's mechanical arm to send out binary signals.

Usually, the mechanical arm functions only to read and write data. But when it is in use, it also produces a number of sounds at varying frequencies. These sounds are what DiskFiltration aimed to exploit.

Once the malware is in place, it can control a hard disk drive to generate noise that is encoded with data, like encryption keys and passwords. To capture the sounds, a recording device simply needs to be placed in close proximity to the computer. In the case of the researchers, they used a smartphone to record sounds coming from a hacked hard disk drive.

Once they were able to decrypt the sounds, the researchers found that DiskFiltration can be used to transmit enough binary information for a data stream. The downside is that the process comes with a slow transmission rate of just 180 bits per minute and has a limited effective range of 6 feet.

Hacks are usually carried out at a fast pace so that kind of data rate makes DiskFiltration sound like it's not a threat. However, 180 bits per minute is still enough to swipe passwords or encryption keys. For a full 4,096-bit cryptographic key, the malware would need about 25 minutes to get to work.

Aside from the slow data rate and limited range, the hack will also have to be carried out by an inside man because the target system is air-gapped. This adds to the limitations of DiskFiltration but the risk is still there.

Given that the hack specifically exploits a hard disk drive's mechanical arm, maybe this will give some people enough incentive to make the switch to solid-state drives.

Earlier, Seagate unveiled a solid state drive with 60 TB capacity, dethroning Samsung's 16 TB model for the distinction of the biggest solid-state drive capacity in the world.

Watch DiskFiltration in action below!

Photo: Beltram Nudelbach | Flickr

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