American Express customers trying to gain access to their online accounts Thursday were met with blank screens or an ominous ancient type face.
The company confirmed that its Web site had come under attack.
The assault, which took American Express offline for two hours, was the latest in an intensifying campaign of unusually powerful attacks on American financial institutions that began last September and have taken dozens of them offline intermittently, costing millions of dollars.
JPMorgan Chase was taken offline by a similar attack this month. And last week, a separate, aggressive attack incapacitated 32,000 computers at South Korea’s banks and television networks.
The culprits of these attacks, officials and experts say, appear intent on disabling financial transactions and operations.
Corporate leaders have long feared online attacks aimed at financial fraud or economic espionage, but now a new threat has taken hold: attackers, possibly with state backing, who seem bent on destruction.
“The attacks have changed from espionage to destruction,” said Alan Paller, director of research at the SANS Institute, a cybersecurity training organization. “Nations are actively testing how far they can go before we will respond.”
Security experts who studied the attacks said that it was part of the same campaign that took down the Web sites of JPMorgan Chase, Wells Fargo, Bank of America and others over the last six months. A group that calls itself the Izz ad-Din al-Qassam Cyber Fighters has claimed responsibility for those attacks.
The group says it is retaliating for an anti-Islamic video posted on YouTube last fall. But American intelligence officials and industry investigators say they believe the group is a convenient cover for Iran. Just how tight the connection is — or whether the group is acting on direct orders from the Iranian government — is unclear. Government officials and bank executives have failed to produce a smoking gun.
North Korea is considered the most likely source of the attacks on South Korea, though investigators are struggling to follow the digital trail, a process that could take months. The North Korean government of Kim Jong-un has openly declared that it is seeking online targets in its neighbor to the south to exact economic damage.
Representatives of American Express confirmed that the company was under attack Thursday, but said that there was no evidence that customer data had been compromised. A representative of the Federal Bureau of Investigation did not respond to a request for comment on the American Express attack.
Spokesmen for JPMorgan Chase said they would not talk about the recent attack there, its origins or its consequences. JPMorgan has openly acknowledged previous denial of service attacks. But the size and severity of the most recent one apparently led it to reconsider.
The Obama administration has publicly urged companies to be more transparent about attacks, but often security experts and lawyers give the opposite advice.
The largest contingent of instigators of attacks in the private sector, government officials and researchers say, remains Chinese hackers intent on stealing corporate secrets.
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