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.
