Wednesday, August 20, 2008

Thwarting Data-Loss Via Steganography: 'Double-Stegging'

Sally Adee writes in IEEE Spectrum:

Earlier this year, someone at the United States Department of Justice smuggled sensitive financial data out of the agency by embedding the data in several image files. Defeating this exfiltration method, called steganography, has proved particularly tricky, but one engineering student has come up with a way to make espionage work against itself.

Keith Bertolino, founder of digital forensics start-up E.R. Forensics, based in West Nyack, N.Y., developed a new way of disrupting steganography last year while finishing his electrical engineering degree at Northeastern University, in Boston.

Bertolino’s method turns this technology on itself. The key to jamming steganography, he says, is using steganography—what he calls “double-stegging.” Double-stegging adds some noise, scrambling some of the image’s least-significant bits. “As long as you’re damaging at least some part of the file,” Bertolino explains, the hidden file becomes garbled and cannot be deciphered. If the cat in the picture is just a cat, the file comes to no harm. But a hidden file, once processed by the double-stegging algorithm, will yield only gibberish. “Our results are simple,” Bertolino says. “An extremely high percentage of the hidden files were destroyed.”

More here.


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