A group of purported hackers in the Middle East has claimed credit for problems at the websites of both banks, citing the online video mocking the founder of Islam. One security source called that statement "a cover" for the Iranian government's operations.

The attack is described by one source, a former U.S. official familiar with the attacks, as being "significant and ongoing" and looking to cause "functional and significant damage." Also, one source suggested the attacks were in response to U.S. sanctions on Iranian banks.

Senior U.S. officials acknowledge that Iranian attacks have been the subject of intense interest by U.S. intelligence for several weeks. Last week, the Joint Chiefs of Staff's Intelligence Directorate, known as J-2, confirmed continuing Iranian cyber attacks against U.S. financial institutions in a report described as "highly classified."

[link to openchannel.nbcnews.com]