Steganography Revealed
Date: October 15, 2003Source: Computer Crime Research Center
By:
... use policies that restrict the installation of unauthorized programs on company computers.
Using the tools that you already have to detect movement and behavior of traffic on your network may also be helpful. Network intrusion detection systems can help administrators to gain an understanding of normal traffic in and around your network and can thus assist in detecting any type of anomaly, especially with any changes in the behavior of increased movement of large images around your network. If the administrator is aware of this sort of anomalous activity, it may warrant further investigation. Host-based intrusion detection systems deployed on computers may also help to identify anomalous storage of image and/or video files.
A research paper by Stefan Hetzel cites two methods of attacking steganography, which really are also methods of detecting it. They are the visual attack (actually seeing the differences in the files that are encoded) and the statistical attack: "The idea of the statistical attack is to compare the frequency distribution of the colors of a potential stego file with the theoretically expected frequency distribution for a stego file." It might not be the quickest method of protection, but if you suspect this type of activity, it might be the most effective. For JPEG files specifically, a tool called Stegdetect, which looks for signs of steganography in JPEG files, can be employed. Stegbreak, a companion tool to Stegdetect, works to decrypt possible messages encoded in a suspected steganographic file, should that be the path you wish to take once the stego has been detected.
Steganography is a fascinating and effective method of hiding data that has been used throughout history. Methods that can be employed to uncover such devious tactics, but the first step are awareness that such methods even exist. There are many good reasons as well to use this type of data hiding, including watermarking or a more secure central storage method for such things as passwords, or key processes. Regardless, the technology is easy to use and difficult to detect. The more that you know about its features and functionality, the more ahead you will be in the game.
[1] Steganography, by Neil F. Johnson, George Mason University,
http://www.jjtc.com/stegdoc/sec202.html
[2] http://dictionary.reference.com/search?q=steganography
[3] The Free On-line Dictionary of Computing, © 1993-2001 Denis Howe
http://www.nightflight.com/foldoc/index.html
[4] Applied Cryptography, Bruce Schneier, John Wiley and Sons Inc., 1996
[5] Steganography: Hidden Data, by Deborah Radcliff, June 10, 2002,
http://www.computerworld.com/securitytopics/security/story/0,10801,71726,00.html
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