The group AntiSec says the information was on the laptop of Supervisor Special Agent Christopher K. Stangl from FBI Regional Cyber ActionTeam and New York FBI Office Evidence Response Team, contained in a file named NCFTA_iOS_devices_intel.csv, InformationWeek reported Tuesday.
NCFTA stands for the National Cyber-Forensics & Training Alliance, which the FBI says is "an international model for bringing together law enforcement, private industry, and academia to share information to stop emerging cyber threats and mitigate existing ones."
AntiSec has accused the FBI of using the identification numbers to track Apple users.
The one million posted numbers are just part of 12 million it found on the FBI computer, AntiSec said.
The policy states the company may disclose customer information "if we determine that for purposes of national security, law enforcement, or other issues of public importance, disclosure is necessary or appropriate."