During the past week or so, researchers at NetWitness have reported increased activity on the venerable Rustock botnet, while researchers at Websense flagged a new spam push from the well-known Waledac network. The new spikes in botnet traffic come less than a month after many security research labs reported a downturn in spam activity in the final quarter of last year.
As the new year rolls out, botnet experts say that even though there was a slowdown last quarter, they expect botnet operators to continue their booming business in 2011 -- with some new twists.
In its blog, anti-malware technology vendor Dasient predicts 2011 will bring "a large botnet cyber war" that will be won by Zeus, the Trojan toolkit that became botnet operators' favorite mode of attack in 2010.
"2011 will likely be the year that large botnets will start more aggressively competing to sustain their growth, and users will get caught in the middle," the blog says. "Zeus has proven its ability to grow to sizes more significant than other botnets, and is also one of the more profitable botnets that target financial institutions. Zeus will hold its ground against other botnets that try to attack it."
As botnets become more common, many operators will choose to simply steal infected PCs from other operators, rather than try to build their own networks, says Neil Daswani, CTO of Dasient. This infighting became evident in 2010, when botnet operators began distributing malware that actually patches vulnerabilities on the PCs it infects, making it more difficult for other botnet operators to use those flaws to infect the same PCs. "That sort of thing will probably be even more evident in 2011, and some users may even begin to see its effects," Daswani says. "Once the user's machine is caught in a battle between botnets, it may begin to experience slowness and unreliability that botnets have generally been able to hide in the past."
Another emerging trend is the use of social networks for botnet command and control, says Christopher Elisan, senior research analyst at Damballa, which makes technology for defense against botnets and other advanced persistent threats. "In the past, operators did their command and control using IRC or other channels that were easier to bring down," Elisan says. "But you can't take down a social network."
All of the botnet experts cited the recent surge in politically motivated distributed denial-of-service (DDoS) attacks, such as those in support of WikiLeaks, as a trend that will likely grow in 2011. As Stewart pointed out, some of these attacks are built on "opt-in" botnets that allow users who support a political cause to willingly instrument their PCs to participate. This botnet-building method can be difficult to defend against because the attacks emanate from devices and software not previously recognized to be associated with botnets.
DDoS attacks also change the way botnets are used, Elisan observes. While the operator of a large botnet typically parses out portions of the network to support a number of spam campaigns, a DDoS exploit might use all of the botnet's nodes in a single attack. In the case of the largest networks, this focused tactic can make a DDoS attack nearly impossible to defend against -- a sobering concept for large businesses, which will likely be the next targets, experts say.
On the other end of the spectrum, attackers are increasingly using smaller botnets to fly under the radar of detection mechanisms and infect specific targets, according to observers. "We have seen botnets as small as 10 computers -- the smaller it is, the less footprint it makes, and the harder it is to detect," Elisan says. Some small botnets might be given node names and addresses that are designed to look like everyday network designations, enabling them to hide in plain view of network administrators who don't know what to look for, he notes.
While smaller botnets might be useful for covert data gathering, larger botnets will continue to be used for broader attacks, such as spam campaigns and DDoS attacks, experts say. But are there uses for botnets that haven't yet been conceived?
"I'm convinced that we will see at least one new application for botnets this year that we haven't seen before," Daswani says. "We're already seeing some use of botnets for keystroke logging, and we expect we'll see more audio logging and Web logging as well. There's a lot going on in this space."
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