The attack is being described by the site as the "widest known cyber attacks against Apple-made computers to date". Apple employees were affected when the visited a site for software developers that had been infected. The malware exploited a flaw in Oracle's Java and was used to launch attacks against Facebook.
"This is the first really big attack on Macs," said the source, who declined to be identified. "Apple has more on its hands than the attack on itself."
Cyber-security specialists Mandiant recently reported that a secretive Chinese military unit was responsible for the attack on U.S. companies; however, Beijing has strongly denied the allegations.
An Apple spokesman declined to provide specifics about the attack but provided a statement.
"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," the statement said.
"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."
Apple says it is working closely with law enforcement to find the culprits and will release software today that customers can use to identify and repair infected Macs.