The name, date of birth, hometown, telephone number, school and blood type of every potential Daesh recruit has been handed to UK's Sky News. The documents are forms that Daesh recruits had to fill out before being accepted into the terrorist network.
Sky News reported that a disillusioned ex-member of Daesh gave the broadcaster the memory stick that had allegedly been stolen from the head of the group's internal security police and contained details of unknown jihadis from 50 different countries. The majority of the European recruits are from France, followed by Germany and Britain.
Prospective members had to pick whether they would like to be a soldier or suicide bomber and stipulate if they had an previous "jihadist experience."
Britain's security agencies are examining the leaked documents to verify their authenticity.
If found to be authentic, "the potential for security services identifying unknown terrorists is greatly enhanced," according to Chris Phillips, head of counterterrorism consultancy firm, International Protect and Prepare Security, who told AFP it was a "massive development" and "shows how ISIS [Daesh] is vulnerable to its own people turning against them."
Doubts have been raised over the authenticity of the documents. Wassim Nasr, FRANCE 24 expert on jihadists said on Twitter:
"Perhaps certain information is authentic but the layout of the documents has been altered in order to sell them at a high cost to different buyers."
According to London newspaper the Guardian, German intelligence officials have also obtained the same documents. A spokesperson for the BKA, the German federal police, confirmed the agency had the documents and experts had determined their authenticity.
The man who allegedly stole the documents on a memory stick is a former Free Syrian Army member, who had joined Daesh but had become disillusioned with the group, claiming Islamic rules had collapsed inside the terrorist organization, which had been overrun by ex-soldiers from the Iraqi Baath party.
Security service in Europe believes 5,000 people have traveled to Syria to join Daesh. If these documents are found to be authentic, the figure appears to be a woeful underestimate of the number of terrorists from western countries who have joined the extremist group.
'More Data Sharing'
Following the leak of the Daesh recruitment documents, Britain's Home Secretary Theresa May announced her intentions to strive for better data sharing with the European Union.
"That's why today I'm going to be working to press, within the European Union alongside my French colleagues, for more data sharing," May said in a statement.
Taking into account the serious challenge Daesh extremists pose to the security of the United Kingdom and Europe as a whole, it is highly important that member states work together to counter this threat, she stressed.
The leaked list reportedly features both notorious individuals and previously unknown Daesh supports.