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Covert Channels

Covert Channels. John Dabney. Covert Channels. “. . . any communication channel that can be exploited by a process to transfer information in a manner that violates the system's security policy. National Institute of Standards and Technology

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Covert Channels

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  1. Covert Channels John Dabney

  2. Covert Channels • “. . . any communication channel that can be exploited by a process to transfer information in a manner that violates the system's security policy. • National Institute of Standards and Technology • “a path of communication that was not designed to be used for communication.” - Matt Bishop

  3. Steganography • “the practice of concealing information in channels that superficially appear benign.” • “While cryptography is about protecting the content of messages, steganography is about concealing their very existence.” – Fabien Petitcolas

  4. Properties • Existence • Hide the fact that communication is taking place • Bandwidth • Unused • Detectability • Evaluation • Ease of implementation • Range • Permissibility • Probability of detection • Anonymity • “Unobservable” • “Unlinkable”

  5. Usage • Network • Wireless - Corrupted headers • Modifying header fields • Optional/mandatory – bits used infrequently raise risk of detection • Modifying existing traffic • Audio and Video stenograms • Encryption • Canary trap and Digital watermarking

  6. An example • http://www.petitcolas.net/fabien/steganography/image%5Fdowngrading/

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  14. Detection • Comparison with original • Artifacts from applications used to hide information • Statistical analysis • Wireless - High error rates

  15. Mitigation • Not complete elimination • Isolation • Bandwidth - time • Randomness/Uniformity • Compression • Changing formats • Disabling certain traffic

  16. Questions? • ?

  17. Bibliography • Bishop, Matt. Introduction to Computer Security. Massachusetts: Pearson Education, Inc., 2005. • “Canary Trap.” Wikipedia. http://en.wikipedia.org/wiki/Canary_trap. April 26, 2007. • “Covert Channels.” Wikipedia. http://en.wikipedia.org/wiki/Covert_channel. April 26, 2007. • Dunbar, Bret. A detailed look at Steganographic Techniques and their use in an Open-Systems Environment. SANS Institute. 01/18/2002http://www.sans.org/reading_room/papers/download.php?id=677&c=29cae459acbc32dac569453048050082&portal=67dfc17e34bed372c83983ad0cbd5629. April 26, 2007. • Owens, Mark. A Discussion of Covert Channels and Steganography. SANS/GIAC GSEC 1.3. March 19, 2002. http://www.sans.org/reading_room/papers/download.php?id=678&c=29cae459acbc32dac569453048050082&portal=67dfc17e34bed372c83983ad0cbd5629. April 26, 2007. • Petitcolas, Fabien. “the information hiding homepage digital watermarking and steganography.” (Nov. 2006) Fabien a. p. petitcolas. http://www.petitcolas.net/fabien/steganography/image%5Fdowngrading/ April 26, 2007. • Sbrusch, Raymond. Network Covert Channels: Subversive Secrecy. SANS Institute. http://www.sans.org/reading_room/papers/download.php?id=1660&c=29cae459acbc32dac569453048050082&portal=67dfc17e34bed372c83983ad0cbd5629. April 26, 2007 • “Steganography.” Wikipedia. http://en.wikipedia.org/wiki/Steganography. April 26, 2007. • Wingate, Jim. The Perfect Dead Drop: The Use of Cyberspace for Covert Communications. BackBone Security.com. http://www.infosec-technologies.com/steganograph.pdf. April 26, 2007.

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