What is Morphing Virus/Polymorphic Virus

1.

These are viruses that are undectable by virus detectors because they change their own code each time they infect a new computer; some change their code every few hours. A polymorphic virus is one that produces varied but operational copies of itself. A simple-minded, scan string-based virus scanner would not be able to reliably identify all variants of this sort of virus. One of the most sophisticated forms of polymorphism used so far is the “Mutation Engine” (MtE) which comes in the form of an object module. With the Mutation Engine, any virus can be made polymorphic by adding certain calls to its assembler source code and linking to the mutation-engine and random-number generator modules. The advent of polymorphic viruses has rendered virus-scanning an ever more difficult and expensive endeavor; adding more and more scan strings to simple scanners will not adequately deal with these viruses. Learn more in: Developments and Defenses of Malicious Code