Computer virus and other malicious code such as worms, bots, and Trojans belong to a class of software known as malware. However, computer viruses are different from the other malicious code in that they propagate themselves in a computer system by inserting a copy of themselves and becoming as part of another program. Unlike other malicious codes such as worms which act as standalone programs and a host program is not necessary for them to propagate, computer viruses spread from one computer to another by attaching themselves as executable files implying that they spread to another computers when a user opens the malicious program or file. Unlike Trojans which does not self-replicate, computer viruses can replicate and overwrite other computer programs by inserting a copy of themselves which also causes destruction to the host program. Sharing of documents through a network, or infected e-mail attachments can cause the spread of computer viruses. Viruses can be transient, resident, and appended viruses. Transient viruses have a life that relies on the life of the host. A resident viruses locate themselves in memory and remain active as stand-alone program even when the host program ends. An appended viruses attach themselves to a host program when the virus is activated when the program is run. Viruses and other malicious codes slow down the performance and productivity of computers by taking up computer resources such as CPU and memory hence slowing down their performance.
Attacks by viruses and other malicious codes can offer fundamental lessons of ensuring that the source of every program should be verified in order to ensure that it does not contain any malicious code that might cause harm to computer systems (Pfleeger, 2003). In addition, it is important to note that malicious code can exist in various forms that might trick the user by appearing as a genuine computer program.
- Pfleeger, S. (2003). Program Security. InformIT. Retrieved 10 May, 2015 from http://www.informit.com