Andy Müller-Maguhn, Laura Poitras, Marcel Rosenbach, Michael Sontheimer and Christian Grothoff: Treasure Map: The NSA Breach of Telekom and Other German Firms (Heinz Leitner)

http://www.spiegel.de/international/world/snowden-documents-indicate-nsa-has-breached-deutsche-telekom-a-991503.html