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What are Computer Viruses and its Types?

March 14th, 2011

Similar to a contagious organic agent that grows up and proliferates in living cells, a computer virus is hard to purge after it has attacked a PC. So it is important to have an idea about the different types of viruses.

Types of Computer Virus

Program Viruses: These infect the executable files and are loaded in memory during the execution, taking the virus along. The virus gets active in memory, forming copies and getting files infected.

Boot Virus: This one is a computer virus that usually infects the boot sector on floppy disks, hard disks, and supposedly also the other bootable media like DVD or CD. As soon as the infected PC boots the virus attacks floppies and other types of media when they are used. Boot viruses are not common these days because floppy disks are not used much.

Multipartite Viruses: Also called multi-part virus, these types of viruses attempt to attack both the executable, or program files and the boot sector concurrently. When virus attaches to boot sector, it will in turn affect the PC’s files, and when the virus bonds to files, it will attack the boot sector. This virus can infect a system again and again if all parts of the virus are not wiped out.

Stealth Viruses: These types of viruses use certain techniques to dodge detection. They might redirect the disk head to read another sector rather than the one where they reside or they may modify the reading of the size of infected file shown in the directory listing.

Polymorphic Viruses: Polymorphism means “several forms”. A basic example for this in programming is function overloading. A polymorphic virus usually uses a polymorphic code, that is, the program uses an intricate algorithm to change the makeup of the internal code whilst maintaining its core function.

Macro Viruses: A macro virus is a new one among the types of computer virus, and infects the macros within a template. When you unlock a spreadsheet or word processing document, the macro virus gets into Normal template. Each document you open points to Normal template, and therefore gets infected with the macro virus. As this virus attaches itself to documents, the attack can spread if the docs are opened using another PC.

This is just a quick glance on types of computer virus. There are a lot of more specialized types. However this info is sufficient for the common user to be more prepared to protect the PC.



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