Dark Reading

Upping its output of spam by nearly 5 percent in recent weeks, a new botnet called Festi has grabbed the attention of researchers, cracking the list of top 10 most prolific spamming botnets, according to Symantec's MessageLabs Intelligence team.

Festi, which the researchers first started watching closely in August, is currently sending an average of 2.5 billion spam messages a day around the world -- mostly pharmaceutical spam, including male-enhancement and herbal remedies, as well as jewelry and watches. The botnet has apparently pumped up the volume of spam by recruiting more bots, about 60 percent of which are in Asia, 18 percent in Europe, and 9 percent in North America, according to MessageLabs.

And its spamming volume jumped significantly during the past few days.

"Festi had been fairly invisible in terms of the amount of traffic it was sending out -- each time we would look at it...it was not featured in the top 10 [spamming botnets]," says Paul Wood, senior analyst for MessageLabs Intelligence and Symantec Hosted Services. "We were quite surprised when it started increasing in significant volume over the last few days."

But while Festi's growth is impressive -- and it's now at the No. 5 slot -- it's still not in the league of the top five spamming botnets. According to MessageLabs, Grum accounts for 23.2 percent of all spam; Bobax, 15.7 percent; Cutwail, 11.1; Rustock, 10 percent; and Bagel, 8.2 percent. MegaD accounts for 6.8 percent of all spam, according to MessageLabs.

Joe Stewart, a researcher with SecureWorks' Counter Threat Unit and a botnet expert, says Festi "looks like it's up-and-coming."

SecureWorks has a slightly different order in its top five botnets, with Cutwail at No. 1, followed by Rustock, Xarvester, Grum, and MegaD. Stewart says of the spam he monitors, Cutwail, which has a half-million bots, sends 65 percent of spam.

Festi likely infects its victims via drive-by downloads, Stewart says, and it's somewhere around 25,000 bots. Its malware is a kernel-based spam bot, too, which isn't typical. "It's a little unusual when you see a brand-new spam bot come out already using rootkit capabilities and running directly out of the kernel," Stewart says. "That suggests this person already [may] have...some experience with spam systems."

The good news about Festi is that it's mostly a spamming botnet, with no malicious, data-stealing malware.

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