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OpenRCE Article Comments: The Viral Darwinism of W32.Evol

Article Abstract The W32.Evol virus was discovered around July 2000. Its name is derived from a string found in the virus, but much more can be implied from the name. Up until then, most of the viruses were using Polymorphic engines in order to hide themselves from Anti-Virus scanners. The engine would encrypt the virus with a different key on every generation, and would generate a small, variant decryptor that would consist of different operations but remain functionally equivalent. This technique was beginning to wear out as AV scanners would trace virus-decryption until it was decrypted in memory, visible and clear.

This article explores the features and functionality of the metamorphic engine of the Evol virus, the first virus to utilize a 'true' metamorphic engine according to Symantec.

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Article Comments
nico Posted: Wednesday, February 21 2007 15:35.17 CST
Good work, interesting disassembly :)

eraser Posted: Monday, March 12 2007 11:13.59 CDT
Many thanks for your valuable contribution.

MazeGen Posted: Friday, March 30 2007 02:57.38 CDT
Very interesting article, thanks.

There's one error in chapter "II. Alternative Instruction Encoding": EB imm8 is JMP short (there's nothing like CALL short).

eraser Posted: Wednesday, April 4 2007 13:33.07 CDT
You are right MazeGen.


EB cb JMP cb  Jump short (signed byte relative to next instruction)
E9 cv JMP cv  Jump near (vword offset relative to next instruction)

Orr Posted: Friday, April 6 2007 16:02.00 CDT
The mistake is in the paper and not in the engine. You can refer to the label 'isJccShort' in the disassembly.

adityaks Posted: Wednesday, June 20 2007 06:07.58 CDT
nice one man

nEINEI Posted: Friday, November 27 2009 04:04.08 CST
good work~~


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