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A polymorphic engine (sometimes called mutation engine or mutating engine) is a software component that uses polymorphic code to alter the payload while preserving the same functionality. Polymorphic engines are used almost exclusively in malware , with the purpose of being harder for antivirus software to detect.
Polymorphic algorithms make it difficult for such software to recognize the offending code because it constantly mutates. Malicious programmers have sought to protect their encrypted code from this virus-scanning strategy by rewriting the unencrypted decryption engine (and the resulting encrypted payload) each time the virus or worm is propagated.
Metamorphic code is used by computer viruses to avoid the pattern recognition of anti-virus software.Metamorphic viruses often translate their own binary code into a temporary representation, editing the temporary representation of themselves and then translate the edited form back to machine code again. [1]
The Smeg Virus Construction Kit (or SMEG) is a polymorphic engine written by virus writer Chris Pile, known as The Black Baron. SMEG is an acronym for Simulated Metamorphic Encryption Generator. SMEG is an acronym for Simulated Metamorphic Encryption Generator.
A polymorphic packer is a file binder with a polymorphic engine. It thus has the ability to make its payload mutate over time, so it is more difficult to detect and remove. [ citation needed ]
However, some developers may employ code obfuscation for the purpose of reducing file size or increasing security. The average user may not expect their antivirus software to provide alerts about an otherwise harmless piece of code, especially from trusted corporations, so such a feature may actually deter users from using legitimate software.
In a predicative type system (also known as a prenex polymorphic system), type variables may not be instantiated with polymorphic types. [1]: 359–360 Predicative type theories include Martin-Löf type theory and Nuprl. This is very similar to what is called "ML-style" or "Let-polymorphism" (technically ML's Let-polymorphism has a few other ...
Interest in polymorphic type systems developed significantly in the 1990s, with practical implementations beginning to appear by the end of the decade. Ad hoc polymorphism and parametric polymorphism were originally described in Christopher Strachey's Fundamental Concepts in Programming Languages, [5] where they are listed as "the two main classes" of polymorphism.