Worm

A type of malicious software that can destroy the computer’s hard drive, files, and programs in memory, and that replicates itself to other disks. Selfreplicating, malicious code that attaches itself to an application program or other executable system component and leaves no obvious signs of its presence. The oldest form of malicious code objects that plague cyberspace. Once they are in a system, they attach themselves to legitimate operating system and user files and applications
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Virus that attacks the MBR. When the system reads the infected MBR, the virus instructs it to read and execute the code stored in an alternate location, thereby loading the entire virus into memory and potentially triggering the delivery of the virus’s payload.
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A computer program that is apparently or actually useful and contains a trapdoor or unexpected code. A malicious code object that appears to be a benevolent program, such as a game or simple utility that performs the “cover” functions as advertised but also carries an unknown payload, such as a virus. Program containing hidden code allowing the unauthorized collection, falsification, or destruction of information. (. See malicious code. )
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A virus that modifies its own code as it travels from system to system. The virus’s propagation and destruction techniques remain the same, but the signature of the virus is somewhat different each time it infects a new system.
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In an encrypted virus, a short segment of code that contains the cryptographic information necessary to load and decrypt the main virus code stored elsewhere on the disk.
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