According to this article, his area was "protection of German soldiers abroad" (which probably means Afghanistan, because we don't have them abroad in many other places). But the most farcical thing is how he got caught. So, if you're curious at the current salary the CIA pays to double agents: according to the FAZ article I linked, "during a first meeting in Salzburg he received 10.000 Euro, a contact email and his first couple of tasks. During two later meetings in Austria his contact paid him 5000 and 10.000 Euro." (If you're wondering why they met in Austria, the BND has their headquarters in Pullach, which is a Munich suburb. You can be in Salzburg in one or one and a half hours if the traffic is good.) All in all, he handed over around 200 documents to the US. And then he got (even more) greedy and offered the Russians to spy for them as well, at which point the BND finally caught him (this was two years after he'd started working for the Americans), because: "He sent three BND documents via email to the Russian consulate to prove his offer was genuine. As part of the internal BND security it could track in which unit exactly these documents were stored, which limited the number of suspects. Since the documents were mailed from a private PC and the man in question had been the sole co-worker officially on vacation at the time the email was sent, he was outed as the mole."

See, this is what I meant in my post about our homegrown spies being rubbish. Emailing the Russians with a job offer from your own personal PC, GOOD LORD. What would George Smiley and Karla have to say to this?!?