Although Intel didn't explicitly tie the hack to the Operation Aurora hack that targeted over 30 companies last year and was discovered in January, it nevertheless made explicit reference to successful attacks on its own infrastructure that occurred around the same time.

"These attempts, which might be the result of industrial or other espionage, or actions by hackers seeking to harm the company, its products, or end users, are sometimes successful," said Intel. "One recent and sophisticated incident occurred in January 2010 around the same time as the recently publicized security incident reported by Google."

The company identified such attacks as risk factors that are admissible to the market.

"The theft and/or unauthorized use or publication of our trade secrets and other confidential business information as a result of such an incident could adversely affect our competitive position and reduce marketplace acceptance of our products."

Although discovered in January and admitted most publicly by Google, Operation Aurora is now thought to have started last April. Adobe also admitted to being targeted by the attack, which sought intellectual property largely consisting of source code. Reports by the Washington Post suggest that Yahoo, Symantec, Juniper Networks, Northrop Grumman and Dow Chemical were also focal points for the hacker.