MI5 has been secretly collecting vast quantities of data about UK phone calls for the last 10 years. According to a report on BBC News, the newly-revealed programme was "so secret that few even in MI5 knew about it, let alone the public." Meanwhile, as part of GCHQ's continuing charm offensive to bolster the case for wider surveillance powers, a senior officer named "Peter" has taken the unusual step of writing an article in The Guardian. In it, he claims "GCHQ cannot and would not hoover up every piece of information," despite evidence to the contrary.

GCHQ vs. MI5 vs. MI6 GCHQ, MI5, and MI6 are all similar but distinct intelligence agencies of the UK government. GCHQ, MI5, and MI6 are all similar but distinct intelligence agencies of the UK government. GCHQ deals mostly with communications intelligence (signal interception and the like). MI5 deals more with domestic human intelligence, while MI6 is more concerned with human intelligence abroad. They all work quite closely with each other: MI5 might use signal intelligence from GCHQ, for example.

For example, drawing on Snowden's leaks, The Guardian wrote in June 2013: "The sheer scale of [GCHQ]'s ambition is reflected in the titles of its two principal components: Mastering the Internet and Global Telecoms Exploitation, aimed at scooping up as much online and telephone traffic as possible." The article went on to give some numbers for GCHQ's spying operations carried out on fibre optic cables linked to the UK: "tapped cables had the capacity, in theory, to deliver more than 21 petabytes a day—equivalent to sending all the information in all the books in the British Library 192 times every 24 hours."

More recently, we have learned about Karma Police, which GCHQ itself billed as the "world's biggest" Internet data-mining operation, intended to track "every visible user on the Internet."

Although the GCHQ officer denies that his organisation engages in mass surveillance, he does admit it has "bulk data powers," which he tries to minimise by claiming: "while the volume we scan may seem large, it is a minute slice of the whole." But as Ars Technica pointed out in 2013, that's a misleading argument: "if properly tuned, the packet analyzer gear at the front-end of [the NSA's] XKeyscore (and other deep packet inspection systems) can pick out a very small fraction of the actual packets sent over the wire while still extracting a great deal of information (or metadata) about who is sending what to whom." The same applies to GCHQ, which can take a "minute slice of the whole," but still get practically everything that really matters.

Finally, Peter tries another, rather imaginative justification for GCHQ's use of these bulk data powers—now dubbed simply "analysing data at scale"—that somehow aren't mass surveillance: "Dealing with encryption and analysing data at scale were crucial for GCHQ’s predecessors at Bletchley Park to succeed in their mission." In other words, if Alan Turing did it, it must be OK. At least he didn't try to claim that James Bond had a licence to scale, as well as to kill.