Update: The New York Times reports that F.B.I has released a statement saying there's no indication that an FBI laptop was compromised or that the FBI sought out the data to begin with.
Hacker group AntiSec claims to have 12 million iPhone and iPad UDIDs it obtained during an attack on an FBI agent's compromised notebook, according to a report in The Next Web. It made 1 million of the stolen UDIDs publicly available in a file posted on Pastebin.
The UDID is a unique 40-digit code assigned to each iOS device and is often used by developers to distribute beta apps to an iOS device. Besides the UDID, some records in the FBI database also contained names, addresses, mobile phone numbers and other identifying information. The group stripped out most of the personal information from the 1 million leaked records, but left the Apple Device ID, Apple Push Notification Service DevToken, Device Name and Device Type, so users can search for their device.