The nation’s major banks came under growing pressure from banking regulators to improve the security of their customer account information after Citigroup Inc. became the latest high-profile victim of a large-scale cyber attack.

While Citigroup insisted the breach had been limited, experts called it one of the first big, direct attacks on a major financial institution, and forecast it could drive momentum for a systemic overhaul of the banking industry’s data security measures.

The Federal Deposit Insurance Corp. (FDIC) is developing new guidance for banks and may ask "some banks to strengthen their authentication when a customer logs onto online accounts," FDIC Chairman Sheila Bair said on Thursday.

Citigroup said late on Wednesday that computer hackers breached the bank’s network and accessed the data of about 200,000 bank card holders in North America.

The nation’s third-largest bank is the latest in a growing list of companies that have suffered cyber attacks, including Sony and Google Inc.

Security experts said the attack may be a watershed moment for the nation’s banking industry, which until now has suffered fewer direct hacker attacks than retailers.

"We’re getting to the tipping point in terms of the number of fraud cases," said Gartner Research security analyst Avivah Litan.

As regulators weigh whether to require more spending on security, "this could be the straw that breaks the camel’s back," she said. (Reuters)