Apple has admitted its staff were caught by hackers exploiting a recent Java zero day browser plugin flaw used to compromise other companies.
"Apple has identified malware which infected a limited number of Mac systems through a vulnerability in the Java plug-in for browsers. The malware was employed in an attack against Apple and other companies, and was spread through a website for software developers," Apple told CSO.com.au.
"We identified a small number of systems within Apple that were infected and isolated them from our network. There is no evidence that any data left Apple. We are working closely with law enforcement to find the source of the malware.
"Since OS X Lion, Macs have shipped without Java installed, and as an added security measure OS X automatically disables Java if it has been unused for 35 days. To protect Mac users that have installed Java, today we are releasing an updated Java malware removal tool that will check Mac systems and remove this malware if found."
Facebook also said its staff were compromised after visiting a website for developers, suggesting the attackers were using the site as a 'watering hole' to attract victims that match a certain profile.
Apple joins a growing list of major tech US brands that have admitted to being hacked in the last month, including Twitter, the Wall Street Journal and the New York Times.
Although Twitter never confirmed its staff were compromised by the Java browser plugin flaw, its director of information security Bob Lord encouraged Twitter users to disable Java in the browser.
About two weeks after the attack on Twitter, hackers targeted Facebook. The attack exploited a zero-day vulnerability in Java that Oracle has since patched. Facebook said it had no evidence any user data had been compromised.
Apple early this month took the drastic measure of blocking the Java browser plugin for the second time in one month using its Xprotect anti-malware system.
Oracle in early February issued an emergency update for Java SE 7 and SE 6, which closed 50 security flaws, most which affected the Java Runtime Environment in desktop browsers. One of the flaws was being exploited, it noted.