At the Ekoparty security conference in Buenos Aires, Argentina, a security researcher has revealed that a hard disk drive (HDD) can be used as rudimentary microphone due to the way of hard drives being designed to work. Check this post for more details.
At the Ekoparty security conference in Buenos Aires, Argentina, security researcher Alfredo Ortega has exposed that a hard disk drive (HDD) can be used as rudimentary microphone to pick up nearby sounds.
That HDD can be used as rudimentary microphone is possible because of the way of hard drives being designed to work. Sounds or nearby vibrations are just mechanical waves that cause HDD platters to vibrate.
How a Hard Disk Drive Is Designed to Work?
Due to its design, a hard disk drive is unable to read or write information to an HDD platter when the HDD platter is moving under vibration. In this case, the hard disk drive must wait until the oscillation stops to perform any operation.
Modern operating systems are equipped with utilities that measure HDD operations. The accuracy is up to nanosecond. Ortega realized that these tools could be used to measure delays in HDD operations.
The delay depends on the loudness of the sound. If the sound is louder, the time of the delay would be longer. These read – write delays enable researchers to reconstruct sound or vibration waves picked up by HDD platter.
Recover Voice May Be Possible
“It’s not accurate yet to pick up conversations,” Ortega said. “However, there is a research that can recover voice data from very low-quality signals using pattern recognition.”
“I didn’t have time to replicate the pattern-recognition portion of that research into mine. However, it’s certainly applicable. For that reason, I would not discard that additional data like voice could be recovered in the future,” the researcher added.
When he was asked that how he came up with the idea to turn his hard drive into a microphone, he pointed out that sound can disrupt hard disk operation. Many hard disk specifications are subject to vibration limitation. This is why they are usually mounted in vibration – proof enclosures made of rubber or other isolating materials. It is easy to infer that HDD can be used to detect sound. But he didn’t expect the delayed response to be proportional to the sound power, which made it a better microphone than he expected.
Hard Drives Can Be Damaged via Sounds
Without limiting his experiment to picking up sounds, the researcher also studied how audio waves affect a hard drive’s mode of operation.
The researcher says that an attacker can use sound waves to launch a resonance attack against an HDD. These types of attacks can result in the hard drive stopping any read-write operations (DOS – Denial of Service) or in physical damage to the device.
In an experiment, he played a 130Hz tone to make an HDD stop responding to commands. “The Linux kernel disconnected it entirely after 120 seconds,” Ortega said.
HDD Resonance Led to Accidents in the Real World
These types of attacks – or rather accidents – happen in the real world. In September 2016, a fire drill involved inert gas deployment led to the shutdown of ING Bank’s main data center in Bucharest, Romania, for about 10 hours.
The sound caused by the deployment of inert gases triggered an unexpected resonance attack, damaging hard disks of the data center and affecting the bank’s operations across Romania, including ATM withdrawals, PoS payments, and network and mobile banking applications.
Ortega is also aware of the Romanian bank incident, and he noted that the attack in his talk used resonance to amplify vibrations, so it only needs a very low volume to cause the same effect. However, with enough energy, any sound will disturb a rotating hard-disk.