In a move that Reuters calls “an unprecedented admission of a widespread cyber-security breach,” Apple (AAPL) on Tuesday admitted that it was the victim of several attacks by the same group of Chinese hackers who previously targeted Facebook (FB) and other large companies. The hackers were able to infect a “small number” of Mac computers that belonged to Apple employees, although it said that “there was no evidence that any data left Apple.” The company plans to release a software tool later today to protect customers from the malicious software used in the attacks. Facebook revealed last Friday that it was the victim of a sophisticated attack by a group of hackers that were traced back to China.