Apple is trying to identify the source of vicious malware attacks on a "limited number" of its Mac systems, a statement from the corporation said.
The corporation is to release new updated software to protect users and its systems.
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.
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.
More top news
Fine for most on Monday but turning increasingly windy
Five people have been rescued from a small leisure boat on the Solent, after its engine failed and it began taking in water.
A US doctor has been accused of killing a lion during an illegal hunt, a week after it emerged dentist Walter Palmer killed Cecil the lion.