On Tuesday, the FBI disputed the Anonymous-affiliate group AntiSec claims that the agency had pilfered the personal details of millions of users of Apple's mobile devices, from the laptop of one of its agents.

The denial by the FBI came after AntiSec hackers substantiated their claims, about the agency's tracking of Apple's mobile devices owners, by posted a link to a database of over 1 million unique identification numbers (UDIDs) for Apple devices - including iPhones and iPads - in March.

The hackers had also asserted that the released database comprised only one portion of the over 12 million UDIDs and personal details which the FBI had gathered from the laptop used by an FBI agent.

However, rebuffing the claims of the AntiSec hackers, the FBI said that it never had the details which have been released; and also added that the validity of the data released by AntiSec could not be corroborated. In fact, federal officials have also extended a warning to computer users to exercise caution while clicking on the AntiSec-posted links, as such links may sometimes contain malware which can infect computers.

While the hackers noted in their post that the released data had been obtained by hacking into an FBI agent's laptop, which contained the data under the file name "NCFTA" - for National Cyber-Forensics & Training Alliance -, the FBI has forcefully countered the allegation saying that there is no evidence to indicate that "an FBI laptop was compromised or that the FBI either sought or obtained this data."