What are virus definitions?
Virus definitions is the common name for a list of viruses stored within your anti-virus software. New viruses are created daily and anti-virus software makers have to constantly battle to keep their virus information current. The way this is done usually is to send out a file that updates your anti-virus software so it can see the new viruses. These updates are called virus definition files.
Virus signature is a sequence of program code which is unique for specific virus or virus family.Antivirus programs rely on virus signatures to detect known viruses.For example the Number Of The Beast virus has the 3-byte signature ‘ 666 ‘ near its end to determine if a file is already infected.What antivirus programs do to see if a file is infected with this virus is looking for that signature in scanned files.Virus definitions specify what signature your antivirus program will look for to detect a specific virus and how the infected files(if there are such) will be cleaned if possible. As trojans and worms don’t infect files,antivirus programs can’t look for a sequence of program code but they will look for specific files or registry keys created by the worm or trojan.If you want your antivirus program to protect you from new viruses you have to download and install the latest virus definitions very often. Antivirus program can’t detect and clean a virus if its signature is not added
