The phenomenal growth of networked computers has fostered the deployment of many network applications such as command and control military communication, Email, web browsing, E-voting, and E-shopping. Many applications need ultra-secure protection. This problem can simply states as: “By the act of communicating, even if perfect confidentiality of the exchanged information is achieved, one can give indications to observing parties of impeding action, capabilities, chains of command, and level of readiness " This book provide a new anonymity mechanism to help hiding user activity over network. The mechanism, named Synthesized Dummy Traffic Generator (S-DTG), is able to synthesize dummy traffic based on samples from real traffic and send it when users are not sending traffic over the network. This mechanism will protect user privacy because it makes it difficult for an intruder to differentiate between periods of users'' activity and inactivity.