Polymorphic viruses are sophisticated file infectors that may build changed versions of themselves in order to avoid detection while maintaining the same fundamental behaviors after each infection. Polymorphic viruses encrypt their programming and employ various encryption keys each time to alter their physical file makeup throughout each infection.
Mutation engines are used by polymorphic viruses to change their decryption routines every time they infect a machine. Because typical security solutions do not use a static, unchanging code, traditional security solutions may miss them. They are considerably more difficult to detect because they use complicated mutation engines that generate billions of decryption routines.
