Antivirus programs, as we know them today, are based on 20-year-old technology of pattern matching. Pattern matching may have worked in the days of the Micheangelo virus and even as recently as Netsky, but methodically matching each and every file on a computer against a list of known malware is getting tedious, if not archaic. In 2007, Symantec detected more than 1 million viruses, with two-thirds created within the calendar year. Loading 1 million signatures, or even a percentage of that if generic signatures are used, is a pretty serious undertaking.
That's why vendors are talking to me about newer strategies for 2009 (and beyond). Among these is the exact opposite of signature file databases--something called whitelisting. If pattern matching is just another way of saying certain bad files have been blacklisted, whitelisting goes to the other extreme: it only allows certain trusted files to run on your machine.
Apparently, because of the growing number of viruses and malware, instead of having signatures of known malware, there will be a whitelist of clean files. Read more http://www.download.com/8301-2007_4-9994679-12.html?tag=fd_morefeatured