Antivirus software is designed to detect, prevent, and remove malicious software, aka malware. The classification of malware includes viruses, worms, trojans, and scareware, as well as (depending on the scanner) some forms of potentially unwanted programs (such as adware and spyware).
At its core, antivirus software provides signature-based detection of malware (malicious software). A virus signature (aka pattern) is based on a unique segment of code within the malware, typically checksummed/hashed and distributed in the form of antivirus signature (aka pattern) updates.
Anti-virus is the name given to software that detects and (where possible) removes viruses from messages. By removing viruses at the email server, all internal mail clients are protected AND all customers are protected from receiving viruses too.
Computer Viruses are written by people who wish to gain control of your system resources and are continually updated to try and break through any barriers you may have installed.
Is your computer safe?