A computer virus is a type of malicious software or malware that can replicate itself and spread by inserting copies of its code into other computer programs or files. When executed, the virus code can damage programs, delete files, or disrupt the operation of the computer. Viruses spread similar to biological viruses by making copies of themselves that get transferred to other computers or storage devices. Common symptoms of a virus infection include programs running slowly, unexpected computer behavior, and files being deleted or corrupted.