Computer security company Finjan Software claims that the current generation of anti-virus software is increasingly ineffective in protecting users against new types of virus software.
The company said that it has discovered seven variants of the SouthPark Worm, a virus that seeks out the address book on a PC and sends copies of itself to as many as 50 other e-mail addresses.
The variants are able to hide from anti-virus software by changing their signatures through compression. This makes them invisible to anti-virus software that looks for files of a specific size and characteristic.
Bill Lyons, CEO of Finjan, said, "There is no way for anti-virus products to ever win the battle against hackers who use compression tools and expanders to create new variants of Trojans and worms."
Finjan is promoting its SurfinShield product which constantly monitors the PC system for unusual activity and blocks any virus without requiring regular virus updates.