US computer security titan RSA Security is offering to replace the SecurID tokens used by millions of corporate workers to securely log on to their computers, The Wall Street Journal reported Monday.

RSA Security chairman Art Coviello told the newspaper in an interview that the company, which was the target of a sophisticated hacking attack in March, was ready to replace the tokens for "virtually every customer we have."

The Journal also said that RSA's parent company, EMC Corp., had acknowledged in a letter to customers on Monday that intruders had breached its security systems at defense contractor Lockheed Martin using data stolen from RSA.

SecurID tokens, which involve constantly changing passwords, are used by thousands of companies to allow employees to securely log on to computers or sensitive software systems.

Coviello did not provide details of the Lockheed incident but the Journal said intruders did not take any Lockheed customer or employee data.

"Their modus operandi led us to believe this perpetrator was likely to attack defense secrets and related intellectual property," Coviello said.

"We believe and still believe that the customers are protected," he said, but as a precaution RSA will offer to replace nearly all of the millions of tokens used by government agencies and businesses.

"I'm not suggesting we won't see some other attacks in the interim given the scale of the Lockheed attack, but it is the only confirmed attack we have using the (stolen) information," he said.

A Lockheed spokeswoman told the Journal that the defense contractor would be replacing all of its SecurID tokens.

Lockheed Martin said last week it had been the target of a "significant and tenacious attack on its information systems network" on May 21.

Headquartered in Bethesda, Maryland, Lockheed Martin employs about 126,000 people around the world.

It focuses on design, development and manufacturing of advanced technology systems, including some of the military's most advanced weaponry.

Lockheed Martin's products include the Trident missile, P-3 Orion spy plane, F-16 and F-22 Raptor fighter jets and C-130 Hercules military cargo planes among many other major weapons systems.

The company is a primary developer of stealth technology used in U-2 and SR-71 reconnaissance aircraft, the F-117 fighter jet as well as the F-35 Joint Strike Fighter designs.

The cyberattack on Lockheed Martin was one of a number of recent hacking attacks.

Sony's online systems have been under attack from hackers since April and Google announced last week that a cyber spying campaign originating in China had targeted Gmail accounts of US officials, military personnel, journalists, Chinese political activists and officials in several Asian countries.