This wasn't off-the-shelf gear, either. A lot of it was "bespoke," or custom-made for GCHQ's operations. In one case, Endace developed a data capture system named Medusa that could intercept data flying by at up to 100Gbps.

It's crucial to note that GCHQ isn't Endace's main customer, or that its products are all intended for unfettered network spying. It has a slew of financial, government and telecom clients, including Verizon (Engadget's parent company), AT&T, Sprint, Bank of America and Morgan Stanley -- and many of them don't have much of a say as to whether or not they use this kind of equipment. Sprint bought a "lawful intercept" system to obtain private customer data only when the police demand it, for instance. The Endace connection is more an explanation of how intelligence agencies like GCHQ can scoop up so much data. It's not necessarily a matter of developing exotic technology in-house. Sometimes, it's just about finding companies whose tech is close enough and asking them to make something more spy-friendly.