Earlier this week, the Izz ad-Din al-Qassam Cyber Fighters threatened to attack Chase, Bank of America, US Bank, PNC Financial Services and SunTrust Bank -- and it appears that the attacks have already begun.

"In new phase, the wideness and the number of attacks will increase explicitly; and offenders and subsequently their governmental supporters will not be able to imagine and forecast the widespread and greatness of these attacks," the hackers warned in a Pastebin post on Monday.

"On Tuesday night, Sitedown.co, which records website outages, had logged roughly 668 reports of people claiming to be unable to log in to their accounts at Bank of America (BCA) within the preceding 24 hours compared with 995 reports in the past seven days," writes American Banker's Brian Browdie. "'We're aware of the reports of possible cyberattacks and we're monitoring our systems, which are fully operational,' Bank of America spokesman Mark Pipitone said in an email. 'We've reached out individually to a small number of customers who reported issues to us yesterday.'"


"The online-monitoring site websitedown.com reported that about noon ET on Dec. 11, SunTrust Banks website suffered intermittent outages," writes BankInfoSecurity's Tracy Kitten. "But SunTrust executives declined to comment on the nature of the outages."

"Some customers of PNC Bank were having trouble logging into their online and mobile banking accounts this afternoon following a threatened digital attack on a handful of big U.S. banks, according to a posting on the Pittsburgh-based bank's Facebook page," writes The Pittsburgh Post-Gazette's Patricia Sabatini. "'We know access to your accounts is important and we continue to address the issue,' PNC said in the post, adding that customers' financial data was secure."