The criminals behind the widespread Conficker worm have released a new version of the malware that could signal a major shift in the way the worm operates.

The new variant, nicknamed Conficker B++, was reported by SRI International researchers, who published details of the new code on last week. At a quick glance, this variant resembles Conficker B. In particular, it is distributed as a Windows DLL file and is packed similarly. Initially, this new version was mistaken for the same worm in different packaging. However, upon further analysis, researchers found that out of 297 subroutines in Conficker B, only 3 were modified in Conficker B++ and around 39 new subroutines were added. Conficker B++ uses new techniques to download software, giving its creators more flexibility in what they can do with infected machines.

Conficker-infected machines could be used for sending spam, logging keystrokes or launching denial of service (DoS) attacks, but a group calling itself the Conficker Cabal has largely prevented this from happening. They've kept Conficker under control by cracking the algorithm the software uses to find one of thousands of rendezvous points on the Internet where it can look for new code. These rendezvous points use unique domain names, such as pwulrrog.org, that the Conficker Cabal has worked hard to register and keep out of the hands of the criminals.

The new B++ variant uses the same algorithm to look for rendezvous points, but it also gives the creators two new techniques that skip them altogether. That means that the Cabal's most successful technique could be bypassed.

Also known as Downadup, Conficker spreads using a variety of techniques. It exploits a dangerous Windows bug to attack computers on a local area network, and it can also spread via USB devices such as cameras or storage devices. All variants of Conficker have now infected about 10.5 million computers, according to an SRI International Technical Report.

Casey Mayville  |  Writer