“During our investigation, we found a small number of computers, including some in our Mac business unit, that were infected by malicious software using techniques similar to those documented by other organizations,” the company said on its Security Response Center website on Friday.
“We have no evidence of customer data being affected and our investigation is ongoing,” it added.
Apple and Facebook were both targeted via a vulnerability in Oracle’s Java platform, and Microsoft said on Friday it was hit by a similar attack.
“This type of cyberattack is no surprise to Microsoft and other companies that must grapple with determined and persistent adversaries,” it said.
The Times, the Journal and Apple each pointed at China as the source of the attacks. Twitter didn’t say where it thought the attacks originated but urged 250,000 of its users to change their passwords.
China has denied involvement in the attacks.
James Niccolai covers data centers and general technology news for IDG News Service. Follow James on Twitter at @jniccolai. James’s e-mail address is firstname.lastname@example.org