Researchers Name Top Six Spamming Botnets

Researchers with Marshal’s TRACE team have identified six botnets that together are currently responsible for distributing 85 percent of all spam, Dark Reading has learned. And the results might surprise you.

Of the six top-spamming botnets Marshal will reveal next week -- Srizbi, Rustock, Mega-D, Hacktool.spammer, Pushdo, and Storm -- the infamous Mega-D and Storm are low on the totem pole. Srizbi is leading the pack, sending 40 percent of spam; Rustock, 21 percent; Mega-D, 9 percent; Hacktool.spammer, 8 percent; Pushdo, 6 percent; and Storm, only about 2 percent.

Marshal earlier this month publicly pegged Mega-D as the king of spam, spewing about 32 percent of the world’s spam and by far overtaking Storm, according to the security firm. Storm was sending about 2 percent then as well, after peaking somewhere around 20 percent in September, Marshal says.

Mega-D -- best known by its male sexual enhancement pill promotions under the names Herbal King, Express Herbals, and VPXL -- later suddenly shut down its botnet after attracting the attention of Marshal and SecureWorks, which analyzed its command and control infrastructure. (See MayDay! Sneakier, More Powerful Botnet on the Loose.)

“That spooked them and they shut down,” says Michael Whitehurst, vice president of global support for Marshal. “But this past weekend, Mega-D fired things up and started spamming again.”

Whitehurst says that even when Mega-D went offline, the male-enhancement spam stayed alive. “The expectation was that the whole Express Herbals/enhancement spam would die out. But it didn’t,” he says. “What we saw was that volume shifted to other botnets. We saw four of the other major spam bots sending it -- Pushdo, Hacktool.spammer, Rustock, and Srzbi. It makes you wonder about the relationship between all of them.”

Marshal, which is identifying some of these botnets by their bot malware names, says there is another 15 percent of malware being sent by botnets that they have not yet pinpointed.

And it turns out botnet size doesn’t matter when it comes to spam distribution. “The size of a botnet isn't necessarily equivalent to the amount of spam it’s generating,” Whitehurst says. “Two weeks ago, the 35,000-bot Mega-D was sending more spam than the 85,000-bot Storm.” (See The World's Biggest Botnets .)

Then there’s the MayDay botnet that Damballa has been closely watching, which can evade leading antivirus products and so far has compromised thousands of hosts, with about 96.5 percent of the infected machines in the U.S., and about 2.5 percent in Canada. Damballa considers MayDay a potential successor to Storm, even though it’s nowhere near as large.

Marshal’s Whitehurst says it’s unclear whether having more bots is actually a handicap in spamming because it's tougher to remain inconspicuous, or whether it’s a matter of which botnet is generating more business for the spammer. “I think we’re one of first groups analyzing what these botnets are producing and how much they are producing, and how that accounts for spam in the world,” he says.

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