It is important to constantly update the anti-virus software on a computer because computers are regularly threatened by new viruses. The anti-virus updates contain the latest files needed to combat new viruses and protect your computer.
Updating Signature Files
Signature files contain the latest list and behavior of known viruses. Anti-virus programs release signature file updates regularly--sometimes daily, sometimes more often--because new viruses are being identified on a daily basis. It is best to configure your anti-virus program to automatically check for updates these updates.
Maintaining the Scan Engine
The scan engine is where the signature files are loaded. It is responsible for scanning and performing actions such as cleaning, quarantining and deleting identified viruses in your computer. Updates on scan engines are intermittent and not as regular as signature files. When a scan engine is updated, it is either to fix a scan engine issue or to make it scan faster, perform better and detect fewer false positives.
Securing Operating Systems
Some anti-virus programs can scan a computer for any vulnerability. Anti-virus software makers have added this feature because security flaws in operating systems are entry points for viruses to hack into the computer. Microsoft's Windows Update automatically checks for vulnerabilities and installs patches on the computer.