Defending against the attacks has been challenging because the servers used to launch them "are being told what to do in real-time," he said. However, the line of attack also "leaves the attackers completely exposed," which is how the U.S. government appears to know who is behind the attacks, he added.
"The attackers have been very brazen. This is being done by someone who doesn't really care about their identify being tracked," Hammack said.
He declined to speculate on the identity fo the attackers.
Retired Rear Admiral Mike Brown, vice president of RSA's federal business group, said there is currently no evidence that the attacks are state sponsored.
"But that can't be counted out of the realm of possibility given the pressure Iran is under from the U.S. and the international community," Brown said. "At the very least, Izz ad-Din al-Qassam appears to be a hacktivist group that is motivated by a nationalist agenda."
He also wouldn't speculate on the identity of the hackers.
Generally, nation states with a serious interest in cyber espionage and cyberwarfare usually employ substantial resources to develop custom malware and exploits for such attacks, he said.
Gartner analyst Avivah Litan noted that U.S. banking regulators such as the Office of the Comptroller of Currency (OCC) have pointed to multiple groups as potential attackers.
"Some are politically motivated and others are financially motivated," Litan said. "Most important, the DDoS attacks have in fact led to or been associated with fraud and customer account takeover," she said.
Regardless of who is behind the attacks, banks need to take them seriously, Litan said.
"They must revisit their network configurations and re-architect them in order to minimize the damage," she said. "For example, they should distribute and decentralize their DNS and Web application servers as much as possible, and set various parameters to deflect the damage that a DDoS attack can do."
The banks must also strengthen backup processes and organizational support to deal with the fallout from such attacks, Litan said. "Banks must deploy layered security and fraud prevention, as outlined in FFIEC guidance to mitigate financial damage from these attacks," she added.
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