Computer systems that are already infected by the Conficker worm are being pushed a new component that kills protective security processes.
In addition, the worm's authors have moved from a 250-a-day domain-generation algorithm to a new one that generates 50,000 domain names every day.
The new version of the worm, also known as Downadup, is being called W32.Downadup.C, and is considered a response to the successful cracking of the W32.Downadup.B worm, according to a post by Peter Coogan on the Symantec Security Response blog.
There is no indication that the new component is designed to spread the worm's infection, just to make it difficult for researchers to counteract on the 10 million machines already infected. Coogan wrote that the worm "does not seem to be using any existing or new means to spread the threat to new machines."
"These early findings may suggest that the Downadup authors are now aiming for increasing the longevity of the existing Downadup threat on infected machines," Coogan wrote. "Instead of trying to infect further systems, they seem to be protecting currently infected Downadup machines from antivirus software and remediation."
The list of security processes that the component attacks include some popular security tools, including wireshark, procmon, tcpview, and regmon. Any processes found on an infected machine that contain such antivirus or security analysis tool strings are killed, according to Symantec.