Annual Computer Security Applications Conference (ACSAC) 2013

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Implementation and Implications of a Stealth Hard-Drive Backdoor

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Modern workstations and servers implicitly trust hard disks to act as well-behaved block devices. This paper analyzes the catastrophic loss of security that occurs when hard disks are not trustworthy. First, we show that it is possible to compromise the firmware of a commercial off-the-shelf hard drive, by resorting only to public information and reverse engineering. Using such a compromised firmware, we present a stealth rootkit that replaces arbitrary blocks from the disk while they are written, providing a data replacement backdoor. The measured performance overhead of the compromised disk drive is less than 1% compared with a normal, non-malicious disk drive. We then demonstrate that a remote attacker can even establish a communication channel with a compromised disk to infiltrate commands and to exfiltrate data. In our example, this channel is established over the Internet to an unmodified web server that relies on the compromised drive for its storage, passing through the original webserver, database server, database storage engine, filesystem driver, and block device driver. Additional experiments, performed in an emulated disk-drive environment, could automatically extract sensitive data such as /etc/shadow (or a secret key file) in less than a minute. This paper claims that the difficulty of implementing such an attack is not limited to the area of government cyber-warfare; rather, it is well within the reach of moderately funded criminals, botnet herders and academic researchers.

Author(s):

Jonas Zaddach    
EURECOM
France

Anil Kurmus    
IBM
Switzerland

Davide Balzarotti    
EURECOM
France

Erik-Oliver Blass    
Northeastern University
United States

AurĂ©lien Francillon    
EURECOM
France

Travis Goodspeed    
United States

Moitrayee Gupta    
University of California, San Diego
United States

Ioannis Koltsidas    
IBM
Switzerland

 

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