computer viruses have caused major financial losses. The actual figures are somewhat speculative, but they were reported as $12.1 billion in 1999, $17.1 billion in 2000, and $10.7 billion in the first three
quarters of 2001 [2]. Thus, obtaining a better understanding of the dynamical spread of computer viruses is an important
issue, which needs to be addressed to improve the safety and reliability of computer systems and networks [3].
Therefore, many studies have proposed solutions that help us to understand how computer viruses operate