A day of disruptions in Wells Fargo & Co.'s electronic banking operations apparently was the latest in a series of cyber attacks that disrupted online operations at Bank of America Corp., Citigroup Inc. and JPMorgan Chase & Co.

A computer security expert blamed massive denial of service attacks, in which perpetrators overwhelm computer servers with communications demands, causing networks to seize up or slow down.

In a posting at Pastebin.com, a group calling itself the Izz al-Din al-Qassam Cyber Fighters claimed responsibility for last week’s outages at Bank of America, Citi, and JPMorgan before hitting Wells Fargo. It said it would attack U.S. Bancorp on Wednesday and PNC Financial Services Thursday.

The posting said the attacks would continue until a video insulting the Islamic prophet Muhammad was removed from the Internet. But computer security expert Dmitri Alperovitch, who has been investigating the attacks, said it could not be determined whether that was the actual motivation.


The posting “appears to be accurate in terms of predicting future attacks,” said Alperovitch, co-founder of the security firm CrowdStrike Inc. “But I wouldn’t necessarily take at face value any of its claims about attribution or the video.”

“It is indeed a very large denial of service attack,” Alperovitch said in an email to The Times.

The long-lasting outages at Wells drew cries of distress from many of the bank’s 21 million online customers and 8.5 million mobile banking users.

“Hey, @wellsfargo.com, what’s up with the website?” one disgruntled customer complained on Twitter. “GoDaddy being down is one thing. You guys being down is an entirely different thing.”


The San Francisco company prides itself on being the first bank in the nation to have provided online account access, and Global Finance magazine last month named Wells the best bank offering online account access for the third year in a row.

The bank responded with apologies online, saying it was working to resolve the problems. It offered no details on how many people had been affected and, as of 9 p.m., provided no estimate of when it might have its online services restored.

“We apologize to customers who may be experiencing intermittent access issues to wellsfargo.com and online banking,” the bank said in an email to The Times. “We are working to quickly resolve this issue. Customers can still access their accounts through our ATMs, stores and by phone.”

Wells Fargo technology and operations spokeswoman Sara Hawkins declined to elaborate.

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