The ability to identify email addresses, phone numbers and passwords impressed the BfV who fancied the software for themselves so struck a deal with XKeyscore to exchange data for computer software. A document called "Terms of Reference" was subsequently produced detailing the agreement.
Two years later, the "Terms of Reference" document has been scrutinized by German media. According to Die Zeit, the document said: "The BfV will: To the maximum extent possible share all data relevant to NSA's mission".
Die Zeit also reports that being given the software by the NSA was "proof of trust". Another agent said XKeyscore was a "cool system".
But the data sent back to the NSA in exchange remains unknown and unaudited outside BfV circles, which has caused further frustrations for German politicians.
"Once again, I have to learn from the press of a new BfV-NSA contract and of the impermissible transfer of data to the US secret service", Green Party parliamentarian Hans-Christian Strobele told Die Zeit.
The existence of the surveillance software and its potential for security agencies to sift through swathes of internet metadata, collecting intricate details of certain targets' conversations was initially revealed by whistle-blower Edward Snowden.
Germany agreed "To the maximum extent possible share all data relevant to NSA's mission." https://t.co/gxIaDumyVd— Free Snowden (@couragesnowden) 26 августа 2015
Controversial communication between the NSA and the BfV reveals that the NSA put pressure on Germany to use the software "productively" to provide "working results" for American spies. Meanwhile the German Federal Office for the Protection of the Constitution says that it operated within the law.