The website for Capital One was inaccessible for online banking customers for hours overnight, possibly the latest salvo in a long-running cyber protest targeting major Western financial institutions over an anti-Islam movie.

Though some customers had reported problems accessing the site over the past 48 hours, Capital One's technical support told ABC News the site went down Wednesday night. As of this report, the website appears to be back up and running.

Wednesday morning a group of online protesters calling themselves the al-Qassam Cyber Fighters announced on a blog Capital One was among their latest victims in a months-long campaign of cyber attacks meant to disrupt the websites of major banks like PNC, Bank of America and JP Morgan Chase. The group is believed to use a relatively unsophisticated tactic called Distributed Denial of Service (DDoS) attacks, which basically flood the target website with so much traffic that it temporarily crashes. Such attacks do not actually breach the target's network security and, in the case of online banking, cannot pilfer any personal or account information.

A spokesperson for Capital One said that "like many other banks, Capital One experienced intermittent access issues on our online bank servicing system." The spokesperson blamed the disruption on a denial of service attack, but said service was "quickly restored."

Al-Qassam also recently announced that a smaller bank, Huntington, had been added to its list of targets. Huntington's website was temporarily disabled this morning but also appears to have recovered. A spokesperson for the bank said no personal information was compromised in the apparent attack.

A self-described spokesperson for the al-Qassam Cyber Fighters told ABC News in November that the point of the cyber campaign is to make the U.S. government force YouTube to take down the "Innocence of Muslims" movie and trailer - a super low-budget, privately-made film that portrays the Prophet Mohammad as a fraud and pedophile. The same movie sparked real-world protests in more than a dozen countries in September.

U.S. officials, including former Homeland Security Chairman Sen. Joseph Leiberman (I-Conn.), have said they believe Iran is behind the cyber attacks. Both al-Qassam and Iran denied that allegation.

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