But to be able to fight the enemy, one must know his face – which are malicious programs and how they work. In a rough approximation of a virtual plague can be divided into three categories: Worms. Used for propagation network resources. Not by chance the name of this class was because of the ability of worms crawl from computer to computer, using networks, email and other communication channels. Given its small size, the worms have an exceptionally high rate of proliferation. An unprotected computer can and minutes do not elaborate on the network.
Propagation method is simple: Worms penetrate a computer, calculate network addresses of other computers and send to these addresses their copies. In addition to network addresses are frequently used address book data mailers. Some of these malicious programs often create working files on disks, but can not any system resources except ram. In this and the difficulty of detection. They seem to leave no obvious traces.
Viruses. Well-known programs that infect other programs by adding them to your code to gain control of all applications or a computer. Viruses spread somewhat lower than worms. Trojans or Trojan horses. They perform on computers to unauthorized users action. For example, deleting information on hard drives, the system to hang, stealing confidential information. In this case, Trojans are not viruses in the traditional sense of the term. They do not infect others program and, as a rule, are unable to penetrate the computers, and distributed attackers disguised as useful software.