... increasingly developed and becomepart of our everyday life It is a very fast and convenient way for us to get information.We can also comunicate with friends and relatives by means of e- mail or ... chatting,people you the Internet for many purposes: education,communication,entertainment and commerce. However,the Internet has limitations. It is not only time-consuming and costly but also dangerous ... dangerous because of viruses and bad programs.Moreover, Internet users sometime have to supper various risks such as spam or electronic junk mail and personal leaking, so , while enjoying surfing, be...