An anonymous reader writes "British secret service GCHQ is willing to penetrate the networks of telecoms firms to subsequently use them for spying. German magazine DER SPIEGEL reports GCHQ hacked the machines of Belcacom staff to later use their GRX routers for targeted man-in-the-middle-attacks on people's phones. Belgacom is the biggest telecom in Belgium, and is partly state-owned. DER SPIEGEL publishes three original slides from a GCHQ presentation. They specifically mention targeting 'engineers/systems administrators.'"