polymorphic virus

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polymorphic virus

A virus that changes its binary signature each time it infects a new file. Using a random number generator, a unique key can be created to encrypt each virus download that self extracts and executes when opened. Without an identifiable pattern to match, the only way to discover a polymorphic virus is by its actions (see behavior detection). See self-extracting file.

Also called a "stealth virus," hundreds of thousands of polymorphic Windows viruses are discovered every day. The actual number of antivirus families that generate that many files is perhaps a few thousand. See virus and antivirus program.
References in periodicals archive ?
These included a new shape changing or polymorphic code, which meant that each time the malwares code was issued by the servers controlling it, it was compiled afresh with additional content, making it look like a completely different programme to researchers looking for specific signatures.
To enable polymorphic code, the virus has to have a mutating engine somewhere in its encrypted body.
This presupposes a good knowledge of assembly language and the use of polymorphic code.

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