[kictanet] Conficker/Downadup Evolves To Defend Itself]

alice alice at apc.org
Sat Mar 14 20:33:27 EAT 2009

Conficker/Downadup Evolves To Defend Itself

Worm develops ability to disable antimalware tools, switch domains more 

By Tim Wilson,  DarkReading <http://www.darkreading.com/>
March 12, 2009

The enigmatic Conficker worm has evolved, adopting new capabilities that 
make it more difficult than ever to find and eradicate, security 
researchers say.

In a blog published late last week 
researchers at Symantec said they found "a completely new variant" of 
Conficker, sometimes called Downadup, that is being pushed out to 
machines previously infected with earlier versions of the worm.

The new variant, which Symantec calls W32.Downadup.C, appears to have 
defensive capabilities that weren't present in earlier versions. While 
it spreads in the same manner, "Conficker.C" can disable some of the 
tools used to detect and eradicate it, including antivirus and other 
antimalware detection tools.

W32.Downadup C also can switch domains at a much greater rate, Symantec 
said. "The Downadup authors have now moved from a 250-a-day 
domain-generation algorithm to a new 50,000-a-day domain generation 
algorithm," the researchers reported. "The new domain generation 
algorithm also uses one of a possible 116 domain suffixes."

A report from CA about Conficker.C 
confirms Symantec's findings, although the CA researchers said the jump 
from 500 to 50,000 domains will not occur until April 1.

The ability to quickly switch domains will make it difficult for 
Internet security organizations, such as ICANN and OpenDNS, to block the 
domains used by the worm, industry experts note.

The new variant emerges just as some vendors have come out with tools 
they say will eradicate the worm. Enigma Software today issued a new, 
free tool <http://www.enigmasoftware.com/> that it says will remove 
Conficker.A and Conficker.B from infected machines. A spokesman says the 
company has begun work on the new variant. And BitDefender also is 
offering a free tool <http://www.bdtools.net/> it says will remove all 
variants of the worm.

Perhaps the most disconcerting aspect of the worm is that although it 
has reportedly infected hundreds of thousands of machines, it does not, 
as yet, seem to have a purpose. Although it has been contacting domains 
and spreading itself through various means, security experts say it has 
yet to be given a task -- such as distributing spam or launching a DDoS 
attack -- and researchers are still uncertain as to what it might be 
used for.

And some experts say there may be other exploits that behave like 
Conficker/Downadup. "BitDefender Labs has been seeing an increase in 
worms, like Downadup, that have a built-in mathematical algorithm, 
generating strings based on the current date," says Vlad Valceanu, 
BitDefender's senior malware analyst. "The worms then produce a fixed 
number of domain names on a daily basis and check them for updates. This 
makes it easy for malware writers and cybercriminals to upgrade a worm 
or give it a new payload, as they only have to register one of the 
domains and then upload the files."

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Copyright © 2007 CMP Media LLC <http://www.cmpnet.com/>

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