A massive bot recruitment campaign appears to be behind a record surge early this month in the volume of malicious spam -- from 3 percent of all spam traffic to nearly 10 percent, according to researchers with Marshals TRACE team .
The Srizbi botnet, which has been making bigger waves these days than the fizzling Storm botnet, is the main driver of this malware-laden spam, according to Marshal, which says malicious spam traffic tripled within just one week. Srizbi is behind nearly half of all spam, malicious or otherwise, according to the researchers.
When you see a 9.9 percent jump in one week, thats significant. They either accidentally sent out too much spam or are on an ambitious recruitment drive at the moment, says Bradley Anstis, vice president of products for Marshal. Anstis says he thinks its more the latter.
MX Logic last week reported a worm that had generated over 8 million spam messages in an apparent attempt to recruit bots for Srizbi. (See New Worm Spawns More Than 8M Spam Messages.)
Srizbi still hasnt captured the same amount of attention as Storm, even though its been quietly gaining steam. Last month, Marshal reported that Srizbi was sending over 60 billion spam messages (malicious and non-malicious) each day, more than all other botnets put together. And SecureWorks earlier this year ranked Srizbi as the largest spamming botnet. (See Srizbi Botnet Sending Over 60 Billion Spams a Day and SecureWorks Unveils Research on Spamming Botnets.)
Normally these botnets go under radar, but Srizbi has not operated under normal rules, Anstis says. Malicious spam, mainly for recruiting bots, accounts for only 1 to 2 percent of all spam from most botnets, while Srizbi had been pumping out about 3 percent.
Joe Stewart, director of malware research for SecureWorks, says the spike in nasty spam could have more to do with Srizbi's makeup -- it's technically a collection of botnets. "Keep in mind that Srizbi is multiple botnets, each rented out to different spammers," Stewart says. The increase in spam traffic could just be one of its "customers" conducting a big spam run, according to Stewart.
According to Marshal, one Srizbi spam run for bots contains the first part of the potential victims email address in the subject line, plus a message about the victim looking stupid in a video, which is an attachment that contains the malware. Another tack is Classmates.com spam, where the message tries to tempt the user to click on a link to check a new message or to meet new friends.
Marshal considers the Srizbi botnet one of the biggest Internet threats today. What were trying to do is to get [the industry] to pay attention to it as much as they do to Storm, Anstis says. Were hoping to get a lot more focus on this to help eradicate it.
Have a comment on this story? Please click "Discuss" below. If you'd like to contact Dark Reading's editors directly, send us a message.