US computer security titan RSA said Thursday that hackers broke into its computers and swiped data that could be used to breach defenses of some systems guarded with its technology.

"Recently, our security systems identified an extremely sophisticated cyber attack in progress being mounted against RSA," the firm's executive chairman Art Coviello said in an open letter posted online.

"Our investigation also revealed that the attack resulted in certain information being extracted from RSA's systems."

RSA is the security division of EMC Corporation in Massachusetts.

Some of the pilfered data related to SecurID "two-factor authentication products" that lets computers connecting online reliably identify one another, according to Coviello.

"While at this time we are confident that the information extracted does not enable a successful direct attack on any of our RSA SecurID customers," Coviello said, "this information could potentially be used to reduce the effectiveness of a current two-factor authentication implementation as part of a broader attack."

RSA is alerting its customers and letting them know what steps to take to defend against attacks.

"This breach seems to present a serious security problem for RSA and many of its customers," said Steve Shillingford, chief executive of computer network forensics company Solera Networks.

EMC repels multiple cyber attacks on its computer network daily and has hardened its defenses in the wake of the successful penetration, according to Coviello. RSA is working with authorities to investigate the attack.

"The cyber attack revealed by RSA today underscores the serious and sophisticated cyber threat we face," US Senator Susan Collins, a member of the Homeland Security and Governmental Affairs Committee, said in a statement.

"The threat of a catastrophic cyber attack is real," she continued. "Attacks are happening now."

Computer systems at Congress and US executive branch agencies are "probed or attacked" an average of 1.8 billion times monthly, according to Collins.