Currently, in most virus detection techniques the signature recognition process of unknown viruses are challenging task. The process has become more difficulties after the complexities of the viruses’ structure have developed, as in the Polymorphic computer viruses. This paper reviews and then explains some used techniques to detect the known polymorphic viruses. Besides, the paper contains the review of some biological models for virus detection. Finally, a new biological model for detecting polymorphic viruses is suggested.