This malicious program category largely exploits operating system vulnerabilities to spread itself. The class was named for the way the worms crawl from computer to computer, using networks and e-mail. This feature gives many worms a rather high speed in spreading themselves. It is mostly found in many systems due to not scanning of particular programs.
Programs that infected other programs, adding their own code to them to gain control of the infected files when they are opened. This simple definition explains the fundamental action performed by a virus – infection.
Programs that carry out unauthorized actions on computers, such as deleting information on drives, making the system hang, stealing confidential information, etc. This class of malicious program is not a virus in the traditional sense of the word (meaning it does not infect other computers or data). Trojans cannot break into computers on their own and are spread by hackers, who disguise them as regular software. The damage that they incur can exceed that done by traditional virus attacks by several fold.
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Potentially dangerous applications include software that has not malicious features but could form part of the development environment for malicious programs or could be used by hackers as auxiliary components for malicious programs.
Utilities used to conceal malicious activity. They mask malicious programs to keep anti-virus programs from detecting them. Rootkits modify the operating system on the computer and alter its basic functions to hide its own existence and actions that the hacker undertakes on the infected computer.
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