To penetrate a remote computer and run your copy of Worms use various techniques: social engineering (eg, text, email, encourages open the attached file), failures in the network configuration (eg, disk-based, open for full access), errors in the security services, operating systems and applications. Some worms also possess properties of other types of malicious software. For example, some worms, Trojan horses contain functions or are able to infect executable files on local disk, ie, they are the property of the Trojan programs and / or computer virus. Classic computer viruses in this category are programs that spread copies of itself to resources on the local computer to: the subsequent launch of its code with any actions the user; further introduction to other computer resources. Unlike worms, viruses do not use network services to penetrate other computers.
A copy of the virus gets to the remote computers only if an infected object, for whatever does not depend on the functional reasons, the virus is activated on another computer, for example: when infection drives available virus penetrated files located on a network resource; virus has copied itself to removable media or infected files on it; a user sends an email with an infected attachment. Some viruses contain the properties of other types of malicious software, such as a backdoor Trojan component procedure or destruction of data on the disk. Trojans in this category include programs performing various unauthorized actions: information collection and transfer of an attacker, its destruction or malicious modification, computer malfunction, the use of computer resources in wrong purposes. Certain categories of Trojans cause damage to remote computers and networks, without violating the performance of the infected computer (such as Trojan programs designed for massive DoS-attacks on remote network resources). Keylogger and other malicious programs in this category include: Tools to automate the creation of viruses, worms and Trojans (designers); software libraries, designed to create malicious software; hacking tools hide the code of infected files from the antivirus scan (File Encryption); bad jokes" that make it difficult to work with a computer; programs to report user false information about his actions in the system; Other programs, one way or another intentionally cause direct or indirect damage to this or remote computers.