"The FBI is aware of these possible computer intrusions and has opened an investigation to address the potential cyber threat," FBI spokesman Jason Pack said.
The move comes one day after AT&T acknowledged that a security flaw on its website made it possible for hackers to query its database and uncover the email addresses of customers who had registered to use its mobile broadband service on their iPhone 3G.
"This issue was escalated to the highest levels of the company and was corrected by Tuesday," the carrier said. "We are continuing to investigate and will inform all customers whose e-mail addresses may have been obtained."
The attack on AT&T's web servers resulted in at least 114,000 iPad 3G users' emails being leaked to Goatse Security hackers when batches of iPad ICC-IDs were entered via specially formatted HTTP requests.
The group automated requests of the email address information for a wide swath of ICC-ID serial numbers using a script. Although the exploit revealed the addresses of several prominent government and corporate officials, no other information was revealed as part of the breach.
A representative for Goatse Security told the Wall Street Journal that it 'hasn't heard from law enforcement and that it didn't do anything illegal, so doesn't see why it would.'