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2005 IEEE Symposium on Security and Privacy (S&P'05) (2005)
Oakland, California
May 8, 2005 to May 11, 2005
ISSN: 1081-6011
ISBN: 0-7695-2339-0
pp: 226-241
James Newsome , Carnegie Mellon University
Brad Karp , Carnegie Mellon University
Dawn Song , Carnegie Mellon University
It is widely believed that content-signature-based intrusion detection systems (IDSes) are easily evaded by polymorphic worms, which vary their payload on every infection attempt. In this paper, we present Polygraph, a signature generation system that successfully produces signatures that match polymorphic worms. Polygraph generates signatures that consist of multiple disjoint content substrings. In doing so, Polygraph leverages our insight that for a real-world exploit to function properly, multiple invariant substrings must often be present in all variants of a payload; these substrings typically correspond to protocol framing, return addresses, and in some cases, poorly obfuscated code. We contribute a definition of the polymorphic signature generation problem; propose classes of signature suited for matching polymorphic worm payloads; and present algorithms for automatic generation of signatures in these classes. Our evaluation of these algorithms on a range of polymorphic worms demonstrates that Polygraph produces signatures for polymorphic worms that exhibit low false negatives and false positives.

J. Newsome, D. Song and B. Karp, "Polygraph: Automatically Generating Signatures for Polymorphic Worms," 2005 IEEE Symposium on Security and Privacy (S&P'05)(SP), Oakland, California, 2005, pp. 226-241.
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