Virus writers have adopted a new tactic to try to make sure their malicious programs reach as many victims as possible. Instead of releasing Windows viruses intermittently, many creators of worms and trojans are pumping them out with increasing frequency.
For a while new variants of one virus, called Mytob, were appearing every hour. Some viruses appear in hundreds of different guises. This tactic is designed to fox security firms that use software to scan e-mail attachments for the signatures of known viruses.
The variants are appearing far faster than firms can analyse them and update their scanners to spot the malicious code. The tactic seems to be paying off. Currently, Mytob variants are filling 14 of the positions in the Top 20 threats list collated by security firm Sophos.
News source: Full Article @ BBC News