MI5 crest with colors

MI5 has secretly been collecting vast amounts of data about UK phone calls to search for terrorist connections.

The program has been running for 10 years under a law described as “vague” by the government’s terror watchdog.

It emerged as Home Secretary Theresa May unveiled a draft bill governing spying on communications by the authorities.

If it becomes law, the internet activity of everyone in Britain will be held for a year by service providers.

While GCHQ’s programs were exposed by Edward Snowden, this one by MI5 remained secret.

And in a way that became increasingly awkward for the security service as the drive towards being more open about capabilities picked up pace in the wake of the report by David Anderson, the independent reviewer of terrorism legislation, earlier in the year.

There were hints about the capability in the speech by MI5 boss Andrew Parker the week before the draft Investigatory Powers Bill was published, when he talked about how “accessing data quickly, reliably and at scale is as fundamental to our work…..without communications data for example we could not have detected and disrupted numerous plots over the last decade.”

He, like the home secretary, claimed that bulk communications data was used to “identify, at speed, links between the individuals plotting to bomb the London Stock Exchange in 2010“.

Now – along with other capabilities – the bulk data program is out in the public and up for debate.