Computer network and communication technology have already been widely used in all aspects of our daily life, but the network security problem is getting more and more prominent, while the network wiretap is one of the biggest challenges of the network security. With the security problem caused by network wiretap becoming more serious, how to monitor the network wiretaps has been the primary problem most researchers have been faced with. By using the ARP cheats to monitor network is a kind of quick and convenient method, which is the topic of this thesis as well.