A computer worm is a computer program designed to furtively copy itself into other computers. Unlike a computer virus, which infects other programs in order to transmit itself to still more programs, worms are generally independent and need no host. In fact, worms typically need no human action to replicate across networks.
DoS attack is a type of cyber crime in which an internet site is made unavailable, typically by using multiple computers to repeatedly make requests that tie up the site and prevent it from responding to requests from legitimate users.
Phishing is the act of sending an e-mail that purports to be from a reputable sources, such as the recipient's bank or credit card provider, and that seeks to acquire personal or financial information.
A Trojan horse virus, is a type of malicious computer software (malware) disguised within legitimate or beneficial programs or files. Once installed on a computer system, the Trojan allows the malware developer remote access to the computer, subjection the computer to a variety of destructive or undesired activities.