Cyberattacks on U.S. banks over the last several months reflect a frightening new era in cyberwarfare that corporations are unprepared to battle because of a shortage of experts skilled in building effective defenses, one security expert says.

Since September, U.S. banks have been battling with mixed success distributed denial of service (DDoS) attacks from a self-proclaimed hactivist group called Izz ad-Din al-Qassam Cyber Fighters. Despite its claims of being a grassroots operation, U.S. government officials and security experts say the group is a cover for Iran.

"There is no doubt within the U.S. government that Iran is behind these attacks," James A. Lewis, a former official in the State and Commerce Departments and a computer security expert at the Center for Strategic and International Studies, told The New York Times.Ã'Â

The skill of the attackers goes far beyond typical DDoS attacks conducted by hacktivist groups such as Anonymous. Instead of originating from networks of compromised PCs, bandwidth-clogging, bogus data streaming to banking sites are coming from hijacked Web servers in data centers.

These muscle systems have enabled the attackers to generate as much as 70 gigabits per second of traffic, enough to totter the sites of even the largest financial institutions.

Such state-sponsored attacks demonstrate that cyberwarfare is here. "We've entered a new era and it's pretty frightening in many ways," said Darren Hayes, a computer forensics expert and chairman of Pace University's Computer Information Systems Program. "What's a little bit scary is the fact that we don't have as many skilled professionals who are network forensics analysts or network security people as we should have."

Traditional security technology, such as firewalls, intrusion prevention systems and antivirus software, are "simply meaningless" against the sophistication of state-sponsored attacks, Hayes said. Colleges and universities need to train more students in forensics and security, so that banks and other large corporations can build better defenses, he said.

The ongoing attacks on U.S. banks have intermittently disrupted online operations, sometimes taking the sites down completely for short periods of time. Banks targeted by the attackers have included Bank of America, Citigroup, Wells Fargo, U.S. Bancorp, PNC Financial, Capital One, JPMorgan Chase, SunTrust Banks, Fifth Third Bank, BB&T and HSBC. None of the banks have lost customer data or have had accounts compromised.

[Related stories:Ã'Â Banks can only hope for the best with DDoS attacksÃ'Â |Ã'Â Wells Fargo recovers after site outageÃ'Â |Ã'Â Theories mount on bank attacks, but experts stress defenseÃ'Â |Ã'Â Arab hackers attack Western websites over filmÃ'Â |Ã'Â Best defense against cyberattacks is good offense, says former DHS official]

"These attacks are representative of the longest persistent cyberattack on an industry sector in history -- in fact, nearly every major commercial bank has been affected," said Carl Herberger, vice president of security solutions at Radware.

Another security vendor, Incapsula, recently analyzed DDoS attack code used by Izz ad-Din al-Qassam. The code came from the Web server of a U.K. customer.Ã'Â The server received instructions from a command-and-control server that timed the attacks to occur for periods from seven minutes to an hour. The precise timing made the attacks more effective.

"The botnet [command and control] was commanding it to work in 'shifts,' maximizing its efficiency and ordering it to renew the attack just as the target would start to recover," Incapsula said in a blog post.Ã'Â

The code was designed to multiply itself, so it could take full advantage of the server's capacity, Incapsula said. As a result, the traffic volume produced was much more than a compromised PC in a traditional botnet.

In a Jan. 1 post on Pastebin, Izz ad-Din al-Qassam vowed to continue the bank attacks, which it calls Operation Ababil. On Tuesday, the group said the attacks would continue until YouTube removed an anti-Islam video that mocked the Prophet Muhammad. The video, called the Innocence of Muslims, sparked violent demonstrations last year in many Middle Eastern countries.

Despite the group's demands, security experts and U.S. government officials believe the attacks are actually in retaliation for Western economic sanctions and for cyberattacks on Iranian computer systems. Over the last three years, three sophisticated viruses, Duqu, Flame and Stuxnet, have struck government systems. The Times reported last year that the U.S. and Israel were behind the 2010 Stuxnet attack that damaged centrifuges in Iranian nuclear facilities.

Iran has denied involvement in the bank attacks.

Read more about malware/cybercrime in CSOonline's Malware/Cybercrime section.