Other computer protection methods
Beside antivirus software, virus infection prevention can be assisted by other means such as implementing a network firewall, or utilizing system virtualization. However, only antivirus software is designed specifically to prevent a computer system from known virus infections.

Network Firewall

Network firewalls prevent unknown programs and Internet processes from having access to the system protected; they are not antivirus systems as such, and make no attempt to identify or remove anything, but may protect against infection from outside the firewalled computer or LAN, and limit the activity of any malicious software which is present by blocking incoming or outgoing requests on certain TCP/IP ports. Hence, a firewall is designed to deal with broader system threats that come from network connections into the system, and is not an alternative to a virus protection system.

System Virtualization

This method of prevention is done by virtualizing the working system. By doing so, the actual system prevents itself from being altered by any infection attempt made by viruses. In fact, it prevents from any alteration attempts to the whole system under virtualization. Such as the virtualization is, without any antivirus software the virtual system can still be infected and consequent damages or malicious actions the virus is meant to cause will still occur. But as soon as the system is shut down and restarted, all the changes and damages previously done to the virtual system will be reset. This way, the system is protected as well as the virus is removed. However, any damages to unprotected (or unvirtualized) data (usually another data drive/volume or data on the network connected to the system) will remain. So will the malicious effects it has caused such as data theft or the like.