
Ĭomputer viruses cause billions of dollars' worth of economic damage each year. Motives for creating viruses can include seeking profit (e.g., with ransomware), desire to send a political message, personal amusement, to demonstrate that a vulnerability exists in software, for sabotage and denial of service, or simply because they wish to explore cybersecurity issues, artificial life and evolutionary algorithms. The vast majority of viruses target systems running Microsoft Windows, employing a variety of mechanisms to infect new hosts, and often using complex anti-detection/stealth strategies to evade antivirus software.

Virus writers use social engineering deceptions and exploit detailed knowledge of security vulnerabilities to initially infect systems and to spread the virus. Therefore, it is not restricted by the host program, but can run independently and actively carry out attacks. A computer worm does not need a host program, as it is an independent program or code chunk. When the program runs, the written virus program is executed first, causing infection and damage. The virus writes its own code into the host program.

Ĭomputer viruses generally require a host program.

If this replication succeeds, the affected areas are then said to be "infected" with a computer virus, a metaphor derived from biological viruses.
