At first blush, the recent attacks against major U.S. financial institutions appear to be a textbook case of hacktivism: Under the name "Operation Ababil," a group of alleged Iranian protestors called for supporters to attack banks and Google's YouTube, citing the Internet giant's refusal to take down a movie that offended some Muslims.

Yet the resulting distributed denial-of-service (DDoS) attacks that caused disruptions at major banks -- including Bank of America, JPMorgan, Citigroup, and Wells Fargo -- did not emanate from the widespread home computers of hacktivists, but from hundreds -- or, at most, thousands -- of servers running vulnerable content management software, say security experts familiar with the attacks. Using the servers and customized malware, the attackers leveled between 70 Gbps and 100 Gbps of peak traffic at the targeted sites and tailored the campaign to get around defenses specifically designed to stop floods of data.

The overall picture emerging from investigations into the attack is that of not just a successful campaign by hacktivists, but of something more, says Rodney Joffe, senior vice president and senior technologist at Internet infrastructure provider Neustar.

"This was a very well done attack, and the key thing is that this was not an attack that was easily survivable," he says. "They effectively took down or disrupted major financial organizations."

The details emerging from the investigation contradict the notion that the denial-of-service (DoS) attack came from a multitude of hacktivist computers during Operation Ababil. Using the name "Cyber fighters of Izz ad-din Al qassam," someone -- or some group -- posted a call to action on Pastebin on Sept. 18, calling for Muslims to attack the Bank of America and the New York Stock Exchange. Four days earlier, messages linked to the same group called for attacks against Google's YouTube.

Yet the Web requests from individuals' systems counted for the minority of traffic in the attack, experts say. The servers that formed the backbone of the attack, and which accounted for the majority of the traffic directed at the targets, were content management servers -- most, if not all, running the Joomla CMS, according to sources who asked not to be named. The attackers infected vulnerable content-management servers with a customized version of the "itsoknoproblembro" DDoS toolkit, likely using a vulnerability in the default Bluestork Joomla template.

Reports of compromises started appearing in the Joomla forums in mid-August, far before the release of the controversial movie on YouTube. The timing suggests that the attackers decided to participate in the hacktivist's operation or used the hacktivism as a smokescreen to camouflage their own activities.

[ After years of focusing mainly on the malware used in data breaches and financially motivated hacks, some security experts have begun to turn the spotlight on the attacker himself. See Turning Tables: ID'ing The Hacker Behind The Keyboard ]

The attackers likely had high-profile targets in mind when they created the network of compromised servers, says Dan Holden, director of security for Arbor Network, a network security company.

"I would say this [set of tools] was custom-built and put together for this particular type of attack: going after targets that would have DDoS defenses and would know how to defend themselves," Holden says. "If you compromise the right servers with the right bandwidth, you can be quite successful."

The average DoS attack falls far short of the volume of traffic leveled at targeted sites during Operation Ababil. While Arbor declined to give bandwidth figures, DDoS mitigation firm Prolexic stated that the attack reached 70 Gbps and 30 million packets per second against some of its customers. Another source familiar with the attacks, who asked not to be named, pegged the bandwidth as high as 100 Gbps.

Such volumes far outstrip previous attacks. In a presentation (PDF) at the North American Network Operators Group in February, Arbor's Jose Nazario asserted that large attacks were the new normal, but defined "large" as attacks with sustained bandwidths of 1 Gbps, two orders of magnitude smaller than those leveled at the U.S. financial institutions. More than 40 percent of companies surveyed by Arbor had encountered attacks greater than 1 Gbps, and 13 percent had suffered attack topping 10 Gbps.

Next Page: Government officials worry about size and skill of attacks By co-opting content-management servers, usually hosted systems with large-bandwidth connections to the Internet, the attackers were able to use fewer systems to level a larger volume of bandwidth at the victims. In addition, businesses will likely not shut down the servers very quickly, even in the face of abuse complaints, Neustar's Joffe says.

"If someone said your core enterprise publishing server is being used in an attack, [the security team] would have to get management permission to shut down the server because it would have a business effect," he says. "I can't say the attackers thought it through that way. It could be pure luck, but on the other hand, a good defender would not ascribe it just to pure luck."

The attacks also appeared to penetrate the DoS defenses that most financial institutions have in place as a matter of policy, says Paul Lawrence, vice president of international operations at Corero Network Security.

"Today's DDoS attacks are carried out by a new breed of highly capable cyber criminals who quickly switch to different attack sources as each new attempt is thwarted," Lawrence said in a statement.

The size and skill used in the attacks have government officials worried, as well. U.S. responders have reportedly had a number of closed door meetings, while the European Network and Information Security Agency has put DDoS attacks front-and-center in its Cyber Europe 2012 incident response exercise that took place on Thursday.

"The scenario for Cyber Europe 2012 combines several technically realistic threats into one simultaneously escalating Distributed Denial of Service (DDoS) attack on online services in all participating countries," ENISA stated. "This kind of scenario would disrupt services for millions of citizens across Europe."

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