Srizbi kernel-mode spambot reappears as Pitou

Posted by   Virus Bulletin on   Aug 28, 2014

Malware possibly still in the 'brewing' stage.

In November 2007, we published an article by Kimmo Kasslin (F-Secure) and Elia Florio (Symantec), in which they analysed the 'Srizbi' trojan, notable for being the first malware found in the wild that operated fully in kernel mode. It appears that Srizbi has made a return.

In a whitepaper published today (pdf), researchers at F-Secure describe 'Pitou', a piece of malware that the authors believe is a revival of Srizbi. And while the two families share a number of similarities, as well as the objective to send spam, the researchers considered the change in code significant enough to justify a new name for the latest incarnation.

As cybercrime goes, spam is considered neither particularly advanced, nor very profitable, so it is interesting to see that a number of fairly advanced, though not entirely new, techniques are being used by the trojan. Among these are 'DLL hijacking' by the dropper to escalate privileges, hijacking the BIOS interrupt handler, and the use of a domain generating algorithm (DGA) to communicate with its command and control servers.

Pitou is believed to have spread via drive-by downloads and through a number of downloaders, which themselves were downloaded via malicious spam. However, the malware is nowhere near as widely propagated as its predecessor was, and it is possible that Pitou is still in the 'brewing' stage. This, of course, makes it all the more important to keep a close eye on how the trojan develops; thankfully, the whitepaper provides many technical details.

More details in a Q&A on F-Secure's blog here.

Posted on 28 August 2014 by Martijn Grooten

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