Many users install antivirus software that can detect and eliminate known viruses when the computer attempts to download or run the executable file ( which may be distributed as an email attachment, or on USB flash drives, for example). Some antivirus software blocks known malicious websites that attempt users must update their software regularly to patch security vulnerabilities. Antivirus software does not change the underlying capability of hosts to transmit viruses. users must update their software regularly to patch security vulnerabilities.