A spate of cyber attacks has left American financial institutions vulnerable to electronic terrorism. An organized hacker group, reportedly from Middle East, has disrupted online banking operations in many large US banks. PNC Financial Services (NYSE:PNC) and U.S. Bancorp (NYSE:USB) are the latest in the list.

PNC Bank

Izz ad-Din al-Qassam Cyber Fighters, the hacker group, claimed that it is attacking banks in revenge of an anti-Muslim film that mocks Prophet Muhammad. Earlier they attacked Wells Fargo and Chase Bank. The attackers send so much traffic on the bank’s website that it take customers a long time to log in, or they lose access to their accounts temporarily.

“Some customers do continue to report intermittent issues logging on to online banking,” PNC spokesperson Fred Solomon said today. “We ask that they try again while we work to ensure full access.”

The banks continue to reiterate that the customers’ account security and private information have not been compromised. But the attacks show that how susceptible our banking system is to electronic crime. Experts say that the attackers have warned the respective banks ahead of time through Internet, still the banks couldn’t do anything to prevent it. In the last 10 days, JPMorgan Chase & Co. (NYSE:JPM), Citigroup Inc. (NYSE:C), Bank of America Corp (NYSE:BAC), Wells Fargo & Company (NYSE:WFC), U.S. Bank and PNC Financial Services (NYSE:PNC) have been attacked.

It is still unclear who is behind the attacks. Izz ad-Din al-Qassam is the military unit of Hamas, a political party that is ruling Gaza strip. On Tuesday, the attackers posted a manifesto on the Internet warning that the cyber attacks will continue until the video “Innocence of Muslims” is completely removed from the Internet.

FBI had warned on September 17 of “a new trend in which cyber criminal actors are using spam and phishing emails … to compromise financial institution networks and obtain employee login information.”

Dmitri Alperovitch, a computer security consultant who is investigating the recent cyber attacks, said that the traffic and phony demands on the bank sites were 10 to 20 times higher than the average.

Millions of customers all over the United States remain worried over the possibility of future attacks and their money in the banks.