A common type of malicious software (malware) that, when executed, replicates itself by inserting copies (possibly modified) into other
computer programs, data files or the hard drive's
boot sector; if this replication succeeds, the affected areas by it are often said to be "infected". Viruses often perform some types of harmful activities on infected hosts, such as stealing hard drive's space or the CPU time, accessing private/sensitive information, displaying political or humorous messages on the user's screen, spamming their contacts, or logging user's keystrokes. However, not all viruses carry destructive payloads or attempts to hide.
A good majority of them
target computers running
Windows.
Computer viruses currently cause billions of dollars worth of economic damage. In response, when it was during the
90's decade, it led to the emergence of the billion-dollar antivirus industry, selling anti-malware protection to users.
The
Melissa macro virus is the most famous
computer virus that appeared on spring of
1999. Other well-known viruses also appeared as well.
