Blue Note: How Intentional Acoustic Interference Damages Availability and Integrity in Hard Disk Drives and Operating Systems

Abstract

Intentional acoustic interference causes unusual errors in the mechanics of magnetic hard disk drives in desktop and laptop computers, leading to damage to integrity and availability in both hardware and software such as file system corruption and operating system reboots. An adversary without any special purpose equipment can co-opt built-in speakers or nearby emitters to cause persistent errors. Our work traces the deeper causality of these risks from the physics of materials to the I/O request stack in operating systems for audible and ultrasonic sound. Our experiments show that audible sound causes the head stack assembly to vibrate outside of operational bounds; ultrasonic sound causes false positives in the shock sensor, which is designed to prevent a head crash.The problem poses a challenge for legacy magnetic disks that remain stubbornly common in safety critical applications such as medical devices and other highly utilized systems difficult to sunset. Thus, we created and modeled a new feedback controller that could be deployed as a firmware update to attenuate the intentional acoustic interference. Our sensor fusion method prevents unnecessary head parking by detecting ultrasonic triggering of the shock sensor.

Taxonomy and Challenges of Out-of-Band Signal Injection Attacks and Defenses

“…The term (sensor) spoofing [8], [9], [14], [43] was also Injection [5], [13], [35], [38], [41]- [44] Intentional Interference [5], [10], [12], [36], [38], [40], [42], [49] Non-Linearity [11], [54], [55], [68] Spoofing [8], [9], [14], [43] Other (See Text) [7], [53], [67] avoided for similar reasons: it has an overloaded meaning in authentication contexts and with in-band signal injection attacks [6], [52]. Moreover, it does not capture the physical aspect of injections, and does not accurately describe coarsegrained attacks which lead to saturation of a sensor.…”

“…Although Shahrad et al primarily focused on the effect of the angle of transmission [53], research conducted in parallel more precisely pinpointed the root cause of the issue using Finite Element Analysis [12]. Specifically, it was shown that (audible) acoustic waves "can displace a read/write head or disk platter outside of operational bounds, inducing throughput loss", even though the displacement is of only a few nanometers [12].…”

“…Although Shahrad et al primarily focused on the effect of the angle of transmission [53], research conducted in parallel more precisely pinpointed the root cause of the issue using Finite Element Analysis [12]. Specifically, it was shown that (audible) acoustic waves "can displace a read/write head or disk platter outside of operational bounds, inducing throughput loss", even though the displacement is of only a few nanometers [12]. In addition, in their "Blue Note" paper, Bolton et al also used ultrasonic transmissions to attack the shock sensors which are meant to protect HDDs during sudden drops by "parking the read/write head" [12]: modern HDDs contain "piezo shock sensors or MEMS capacitive accelerometers" to "detect sudden disturbances" [12], and can also be attacked through ultrasound transmissions at their resonant frequencies.…”

“…Through these malicious acoustic attacks, SPL levels of up to 130 dB cause HDDs at distances of 10 cm to become unresponsive, thus disabling laptops and video recorders [12].…”

“…In addition, out-of-band acoustic attacks on MEMS sensors [10], [13] have both inspired and been influenced by in-band optical attacks on unmanned aerial vehicles (UAVs) [52]. Moreover, after the effects of acoustic noise on the security of gyroscopes were first identified [10], subsequent work improved the level of control over the output [43], and attacked additional types of MEMS sensors [13], and electromechanical devices such as HDDs [12].…”