Defending against virus attacks in network is a vital part of network security. With the rapid evolution of viruses, its defense mechanism has also been evolved over the years. But given the diversity and complexity of virus propagation and its attack behavior, no defense mechanism is equipped fully to protect the network from such attacks. Several anti-viruses are available in the market. But none can give full proof solution to malicious attacks in communication networks. In this paper, the authors present a mechanism to measure and compare the relative ability of antivirus against various kinds of viruses. They construct a hierarchical structure for different virus defense mechanism.