Distributed denial-of-service, or DDoS, attacks -- where armies of bots are pointed at a website or servers and instructed to send streams of innocuous traffic in order to overwhelm and ultimately shut down an organization's online presence or resources -- are nothing new. But the bad guys are finding new ways to capitalize on this classic attack that's nearly impossible to prevent and cost businesses in downtime and lost revenue.
Damballa Research's discovery this week of the so-called IMDDOS, a commercial service for DDoS attacks, is now one of the largest active global botnets, according to researchers there. The botnet is made up mostly of infected machines in China, but U.S. machines are in the top 10 countries with infected IMDDOS machines, many of which are from North American ISPs and major corporations.
DDoS-as-a-service is nothing new -- botnet operators traditionally have offered different services via underground forums. "As a potential renter, you would communicate directly with the owner and negotiate through IRC [Internet Relay Chat]," says Gunter Ollmann, vice president of research at Damballa.
But the IMDDOS service operates in plain sight with a website that details the various levels of service it offers. "This is a full-service offering ... they can handle multiple subscribers simultaneously," he says. "This is the next step up on the ladder in sophistication."
Ollmann says the botnet swelled in activity to about 25,000 unique recursive DNS lookups per hour. Damballa doesn't have hard numbers on the bot count, but Ollmann says the botnet is targeting named Web servers. "The malware itself is unsophisticated, but technically it's a multipurpose agent," he says.
Researchers at Arbor Networks are investigating whether IMDDOS is related to another Chinese DDoS botnet they have been watching, YoyoDdos, which has attacked nearly 200 websites, mostly in China, as well as some U.S. sites. "We think that there may be some lineage there with YoyoDdos and other China-based botnet tools, possibly due to shared code," says Jose Nazario, senior security researcher for Arbor.
"'DDoS as a business' is thriving and continues to evolve," says Andre' Di Mino, director of Shadowserver, who has been tracking the BlackEnergy-based botnet DDoS'ing various industries worldwide. "We've seen advances in botnet technology that specializes in DDoS attacks, and there is no shortage of groups that are willing to carry out attacks for a price."
And demand for these services is on the rise, he says. "It's not just extortion anymore. It's also in reducing your competitor's availability, retaliation, or to simply make a statement against a cause or organization," Di Mino says. "DDoS is again evolving into not just a technical consideration -- there are social, political, and economic issues involved as well."
Arbor's Nazario says DDoS has remained a hot attack method during the past few years. The biggest changes in DDoS have been DDoS attackers aiming for the application layer rather than the network layer, at HTTP and DNS. "We think it's a means to cause more load for the effort, dealing with Windows' disabling of raw sockets, and the propagation of code bases that everyone seems to use or copy," says Nazario, who blogged about the Malaysian DDoS attacks this week.
Damballa's Ollmann says DDoS botnets tend to be made up of hand-me-down or recycled bots. "Compromised machines constantly are changing hands. They seem to cycle through different botnet operators specializing in different types of tasks," Ollmann says. "The value of the machine is diminished when it's handed over several times, so you tend to see the bottom rung on hand-me-downs is DDoS."
It's a way for botnet operators to squeeze maximum value out of the bots, he says.
And all the while, the commercial black market for DDoS is growing and becoming more visible, he says, such as the IMDDOS service. Ollmann has published a report that analyzes IMDDOS and its malware, which he says is a unique family of malicious code.
Damballa has been working with authorities to shut down the U.S.- and other government-accessible elements of the botnet, which uses free dynamic DNS provider services out of China, he says.
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