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7. A computer virus attaches itself to the host files and always activate whenever the
infected files are opened. The virus can replicate itself and then infect the other files on
your computer causing more damage.
Viruses can be differentiated by the methods they use to spread. Worms are viruses that
self-replicate and spread via e-mail or networks. Trojans are seemingly legitimate computer
programs that have been intentionally designed to disrupt computing activity or use computer for
something did not intend. Advancement in communication system paved way for the number of
viruses, worms and Trojans and the speed with which they spread have increased dramatically.
Flaws in operating systems like Windows or peer-to-peer file sharing programs and other widely
distributed network software may open "backdoors" to computer and can run malicious code,
infect system, or use computer for their own personal benefit.
Some popular peer-to-peer programs are: Acquisition, Aimster, Ares, Audiogalaxy,
BearShare, BitTorrent (and other BitTorrent clients), Blubster, Direct Connect, eDonkey2000,
Freewire, Gnotella, Gnucleus, Grokster, GTK-Gnutella, iMesh, Kazaa, LimeWire, LordofSearch,
Mactella, Morpheus, NeoNapster, OneMX, Overnet, Phex, Piolet, Qtella, Shareaza, SoulSeek,
SwapNut, TrustyFiles, Warez P2P, WinMX, and XoLoX. Some of these are, no doubt, safer than
others. All of them make your computer more accessible from the Internet.
Backdoors created by spyware may also be vulnerable to viruses. Spyware provides
some kind of service in exchange for monitoring and reporting activities. At a minimum,
spyware is likely to degrade the performance of your computer and increase traffic on your
network connection. It may also result in annoying pop-up advertisements while you surf the
Web. In the worst cases, computers become so clogged with spyware that they are no longer
usable. Ad-Aware from Lavasoft and Spybot Search and Destroy from Safer Networking are two
preferred tools for combating spyware. Both are free for personal use.
Given below is a list of different types of computer viruses and their functions
7.8.2 Types of Computer Viruses
i. Macro Viruses
Macro viruses infect files that are created using certain applications or programs that
contain macros, like .doc, .xls, .pps, .mdb, etc. These mini-programs make it possible to
automate series of operations so that they are performed as a single action, thereby saving the
user from having to carry them out one by one. These viruses automatically infect the file that