The Blaster worm - also known as MSBlast or LoveSAN - had hit at least 330,000 machines around the world as of lasy Thursday afternoon, according to Symantec, which has been tracking the spread of the worm since it first appeared last Monday.
"The actual number is probably much larger," acknowledged Vincent Weafer, senior director for security response at Symantec, which has a worldwide tracking system of firewalls, intrusion detection systems and other equipment to tally an estimate.
Symantec said the count could be as much as a million, making Blaster one of the most widespread computer worms ever, though still probably a bit behind the notorious Nimda, SQL Slammer and Code Red. Another security firm, RedSiren, is pegging the damage in terms of lost productivity related to IT staff detecting and cleaning infected systems to be at least $US320 million alone.
Even as Blaster continued to spread, and was expected to launch a denial-of-service attack against the Microsoft Windows Update site over the weekend, there were concerns among security professionals that a new round of Blaster-like worms was on the way.
So far, there are known to be at least two "B" variants on Blaster that carry Trojans. Up till now there is no evidence that either of these was taking off in the same way as Blaster had so far, both Network Associates and Symantec said.