The Internet community succeeded in cutting off the links that would have allowed the prolific Sobig-F worm to phone home last weekend.
This action prevented the worm downloading new and potentially even more malevolent code onto infected PCs. However, the worm itself is continuing to spread.
As we reported on Friday, Sobig-F includes code that attempts to contact a list of 20 predefined IP addresses on UDP port 8998 on Fridays and Sundays between 1900 and 2200GMT (as explained here). Security experts believed these addresses contained locations from where additional code could be downloaded.
This potential activity produced a major security flap last Friday, when the virus was expected to attempt these actions for the first time, but in the event nothing much happened. The owners of the servers were contacted and all bar one of the 20 master servers were taken offline. The one rogue server that did remain online only did so intermittently and it to was taken offline by the time of the second wave of the attack. An advisory by F-Secure gives a timeline for the attack.
Although the threatened weekend attack proved to be something of a damp squib, the worm itself continues to breed like rabbits on particular potent fertility drugs.
Sobig-F, the sixth in a series of increasing annoying malware variants, is due to deactivate on 10 September but there's no guarantee that an even more prolific virus might be released in its wake. ®
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