Wednesday, April 1, 2009

Attack Of The Mini-Botnets

Via DarkReading -

Big-name botnets like Kraken/Bobax, Srizbi, Rustock, the former Storm -- and even the possible botnet-in-waiting, Conficker -- have gained plenty of notoriety, but it's the smaller and less conspicuous ones you can't see that are doing the most damage in the enterprise.

These mini-botnets range in size from tens to thousands versus the hundreds of thousands, or even millions, of bots that the biggest botnets deploy. They are typically specialized and built to target an organization or person, stealing corporate and personal information, often without a trace. They don't attract the attention of the big spamming botnets that cast a wide net and generate lots of traffic; instead they strike quietly, under the radar.

"There's definitely specialization [in botnets] these days," says Joe Stewart, senior director of malware research for SecureWorks. "There are botnets designed for fraud, and they have been around for a while and don't seem to cross over [with the bigger spamming botnets]," he says.

These mini-botnets specialize in identity theft, fraud, and stealing corporate information, and are much more difficult to spot and infiltrate than a big spamming botnet. "We have to rely on the few anecdotal instances, where we've managed to get a look at the back-end," Stewart says.


The main goal of specialized botnets is to steal user names and passwords, banking credentials, intellectual property, and other valuable information, he says. "We've seen them target banking credentials used by the enterprise to conduct corporate banking," Cox says. "We've also seen particular executives targeted who are involved in intellectual property development and research activities.

"There's a strong tie there between what information the [targeted] employee has access to and the value that asset has to the attacker."

SecureWorks' Stewart says small botnets are more worrisome than Conficker's next move. These botnets include Clampi (a.k.a. Ligats and Rscan), Torpig (a.k.a. Sinowal, Anserin), Zeus (a.k.a. prg/zbot), Pinch (a.k.a. ldpinch), and SilentBanker Cimuz -- all named after the malware they use -- plus one that has been around for some time, Coreflood (a.k.a. Afcore), which Stewart has studied closely. "I am far more worried about some of the recent Clampi [activities] and some of the other ones," Stewart says. "They have made inroads to affect users and do something malicious, like steal their credentials" for committing identity theft and fraud, he says.


Steven Adair, a researcher with the Shadowserver Foundation, says his organization has seen targeted botnet attacks that have used anywhere from dozens to hundreds or more machines. "They are often a lot smaller than the spamming and DDoS botnets due to their target selection," Adair says.

These targeted botnet attacks often use spear-phishing email attacks, using malicious PDF attachments or links that appear legitimate because they contain information familiar to the user. Shadowserver has also seen mini-botnets infect Websites that cater to a specific group of users, Adair says. "The sites were specifically chosen due to their audience," he says.

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