What is a virus?
A computer virus is malware that replicates itself and infects computer data, files, programs, and systems, similar to its namesake that infects human bodies. See also malware.
How does a virus work?
Viruses always attach themselves to other programs. A virus can make a computer slower, steal private information, take up disk space, corrupt data, display messages, spam the user’s contacts, and log their keystrokes. See also keylogger.
Viruses can be guarded against using up-to-date antivirus software.