National security officials told NBC News that the continuing cyber attacks this week that slowed the websites of JPMorgan Chase and Bank of America are being carried out by the government of Iran. One of those sources said the claim by hackers that the attacks were prompted by the online video mocking the Prophet Muhammad is just a cover story.

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.