In a report with the punchy title Blue Note: How Intentional Acoustic Interference Damages Availability and Integrity in Hard Disk Drives and Operating Systems a team of boffins from the University of Michigan and the Zhejiang University used sonic and ultrasonic sounds to disrupt magnetic HDDs as they read or write data.
The researchers showed how the technique could stop some video surveillance systems from recording live streams. Just 12 seconds of specially designed acoustic interference was all it took to cause video loss in a 720p system made by Ezviz. Sounds that lasted for 105 seconds, or more caused the stock Western Digital 3.5 HDD in the device to stop recording altogether until it was rebooted. The attack used a speaker hanging from a ceiling that rested about four inches above the surveillance system’s HDD. The researchers didn’t remove the casing or otherwise tamper with the surveillance system.
The technique was also able to disrupt HDDs in desktop and laptop computers running both Windows and Linux. In some cases, it even required a reboot before the PCs worked properly. The technique took as little as 45 seconds to cause a Dell XPS 15 9550 laptops to become temporarily unresponsive when the laptop played malicious audio over its built-in speaker. When the sound played for two minutes or more, the computer had to be rebooted for the drive to work properly again.
The technique works because audible sound can cause an HDD’s head stack assembly to vibrate outside of normal bounds. The vibrations push the head far enough from the centre of the drive track to temporarily prevent writing. Ultrasonic sound, by contrast, can create false positives for an HDD’s shock sensor, which is designed to prevent a head crash. The attack could be used against computers and surveillance systems and medical devices that use magnetic HDDs.
Of course, there are much easier ways to take down computers temporarily and embedded systems, still it does mean that those workers who insist on playing Coldplay through the terrible speakers on their iPad should be punched in the face twice. Once for endangering your hard drive and another time for lowering the standards of the world.