Polish CERT Takes Action Against Virut Botnet

The computer emergency response team in Poland, CERT Polska, announced last week that they’ve taken over several domains linked to the Virut botnet. While it may not have a long-term impact on the botnets operations, CERT Polska’s actions have certainly delivered a devastating blow to the malware family.

NASK, the operator of the Polish domain registry, took over 23 Virut domains Jan. 17. According to the figures, 890,000 unique IP addresses were reported to have been infected by Virut in Poland alone last year.

The botnet has existed since 2006, and has remained a consistent threat online since then. Kaspersky Lab claimed in a recent report that Virut was responsible for 5.5% of the Q3 2012 malware infections observed by their systems, and Symantec said just this month that some 308,000 systems were actively infected by it.

“Interestingly, Virut’s main distribution vector is executable file infection, and most users would get infected by using removable media or sharing files over networks. However, more recent versions of the malware have been capable of infecting HTML files, injecting an invisible iframe that would download Virut from a remote site… Effectively, Virut’s authors have converted those machines into zombies – elements of a botnet used for spamming, DDoS attacks and other malicious activities,” CERT Polska explained.

Last week, SecurityWeek’s Brian Prince reported on Symantec’s announcement that Virut was spotted distributing the Waledac family of malware, using it to propagate a massive spam campaign. During its analysis, researchers observed a compromised computer sending roughly 2,000 emails per hour. 

“Conservatively, if a quarter of the estimated 308,000 computers infected with W32.Virut download W32.Waledac.D, then potentially billions of spam emails can be sent from these computers,” Symantec’s Security Response Team noted in a blog post. “The following table contains some basic calculations on the estimated volume of emails from this campaign with totals ranging from 1.2 billion to 3.6 billion spam emails per day.” 

Of the domains taken down, zief.pl and ircgalaxy.pl, have been used to host Virut, as well as its command & control IRC servers. Moreover, they were used to host other malware including Palevo and Zeus, Polska noted.