The names, addresses and phone numbers of 22,000 Islamic State recruits have been handed over by a disillusioned member of the organization, Sky News reported Thursday.
The tens of thousands of documents contain the details of jihadis from at least 51 countries.
Applicants had to fill in a 23-question form before they were allowed to join the group.
Sky News obtained the files on a pen drive stolen from the head of Islamic State’s internal security police.
It was taken by a man identified as Abu Hamed, a former fighter for the Free Syrian Army who defected to Islamic State. He then became disillusioned with the group, saying the Islamic rules that inspired him to join had collapsed inside the group.
Sky News said it had informed the authorities of the intelligence haul.