Forbs is reporting that Anonymous and Antisec have dropped a file with a million Unique Device ID (UDID) numbers for Apple iOS devices. They claim to have acquired an additional 11 million records which they may release later.
In addition to the identifiers, the file is said to also contain usernames, device names, cell numbers, and addresses. It is this additional personal information that seems to be the real threat here.
The Next Web has set up a tool for checking to see if your information is in the leaked data. You don't need to enter your full UDID into the field, just the first 5 characters. That way you don't need to trust them with your information either.
None of my iOS devices showed up on the list, so I downloaded the entire file to look it over. You can see the release and download instructions here.
Looking through the document, I don't see any examples of particularly sensitive information. In the first field are the claimed UDID. The second field is a 64 digit hex string. After that is the name of the device, frequently something like "Lance's iPad". Finally is a description of the device itself: iPad, iPhone, iPod touch.
SHA hashes are 64 hex digits long, and are widely used in forensics to verify that captured evidence has not been changed. My intuition is something like that is what we are seeing in that second column.
I have no idea where the claims about addresses, and account names came from. I am not seeing anything like that.
It is interesting that Anonymous / Antisec claim that this data came from the hacked laptop of an FBI agent. This certainly raises big questions about why he would have this information on his laptop, and why the FBI has it at all.
While 12 million is a big number, it is a tiny fraction of the over 400 million iOS devices sold to date. Still, that would represent a shockingly wide dragnet if these are all being monitored in some way by law enforcement.
Of course, for all we know this list was captured evidence from some other group of hackers.
So, short answer (too late!), you probably don't have anything to worry about here, but you might want to check to see if your device is in the database anyway.
UPDATE: It appears that the UDID may tie to more information that was immediately apparent. While Apple's guidelines forbid tying UDIDs to specific account, of course that happens all the time. My friend Steve shared a link with me to an open API from OpenFeint which can tie a UDID to personal information. Certainly there are others which would reveal other information. The existence of these, and the leaked list of UDIDs would allow an app developer to tie a user's real identity to their activity and use of the app on their iOS device.
UDATE 2: I find it impossible to actually read documents from Anonymous and Antisec, they are just so poorly written. It seems I missed their statement in lines 353,354 of the pastbin where they say that they stripped out the personal information. The 64 digit block is actually the "Apple Push Notification Service DevToken". SCMagazine is reporting that the FBI is denying the laptop was hacked or that they have the UDIDs.