Security of wired and wireless networks is the most challengeable in today's computer world. The aim of this study was to give brief introduction about viruses and worms, their creators and characteristics of algorithms used by viruses. Here wired and wireless network viruses are elaborated. Also viruses are compared with human immune system. On the basis of this comparison four guidelines are given to detect viruses so that more secure systems are made. While concluding this study it is found that the security is most challengeable, thus it is required to make more secure models which automatically detect viruses and prevent the system from its affect.