Computer viruses are transmitted from one computer to another when you copy infected data from an external source..They become active when you start an infected application and usually infects any aaplication you run..They are categorized by their targets...
Program Viruses:-these infect program files such as.COM, .EXE, .SYS, .DLL, .OVL or .SCR.
Boot Viruses:- Infect the system areas of hard disks and floppy disks..Boot viruses are very successful than program viruses in infecting their targets and spreading..
Macro Viruses:- these virus infect data files.. Like Microsoft Word documents and template files.. they spread rapidly as nfected documents are shared on networks and downloaded from internt sites..
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