What is a computer virus?

Using anti-virus tools makes detecting and eradicating viruses an easier task. There are many types of anti-virus software, employing several technologies. A common type of anti-virus tool is a "scanner".

Scanners examine every file on a specific disc drive, looking for known virus "signatures". Every virus has a unique signature, which is a string of software code. Drawbacks to scanners include their inability to detect new viruses, and the requirement that the user determines when to initiate the virus scanning process.

Other types of anti-virus tools include those that will run continuously on a system, and those that will run every time the machine is booted.