a self-replicating program that spreads by inserting copies of itself into other executable code or documents. A program into which a virus has inserted itself is said to be infected, and the infected file (or executable code that is not part of a file) is a host. Viruses are a kind of malware (malicious software). Viruses can be intentionally destructive, for example by destroying data, but many viruses are merely annoying. Some viruses have a delayed payload, sometimes referred to a bomb. The primary downside of viruses is uncontrolled self-reproduction, which desecrates or engulfs computer resources..”