According to the documents, leaked by Edward Snowden to the Guardian, the UK’s Government Communications Headquarters (GCHQ) collects vast amounts of data from fibre-optic systems. The scale of the operation is massive, and the use of the data, also shared with the NSA is a big concern.
The project called Tempora aims to attach probes on 90% of the cables running through the UK. In the last 5 heart Tempora is half way - it has access to 200 fibre-optic cables (including the transatlantic traffic), collecting and analysing data from 46 of them.
This adds up to 600 million “communication events” daily when full content of transmissions is preserved for 3 days and metadata for 30.Together the GCHQ and NSA have 550 analysts working with the data and 850,000 officials with top secret clearance can access it. The fact that NSA shares its PRISM data with the UK was not a secret, thanks to Snowden it is known it goes in reverse too.
GCHQ refused to confirm or deny Tempora’s existent even though the leaked document from the exiled Internet spy attesting to it. However the government officials claim that all their actions fall within the legal parameters.
The Guardian cites an unnamed expert with knowledge of intelligence who explained that the fact of interception doesn’t mean that security agents listen to all the calls and read all the internet correspondence — the amount of data is way too massive.