Summary:

(1) GCHQ forces communications companies to allow them to install interception devices on land at international communications cable landing points "where they land on British shores carrying data to western Europe from telephone exchanges and internet servers in north America". (Europe is going to be pissed off!)

(2) NSA/GCHQ feared revealing the identities of those commercial "intercept partners" in this scheme would cause high-level political fallout.

(3) "Some companies have been paid for the cost of their co-operation".

(4) The companies themselves "are forbidden from revealing the existence of warrants compelling them to allow GCHQ access to the cables." (Not a surprise; Assange often points out that the UK is the world's biggest deployer of media gag orders... so why not here?)

(5) This mass tapping operation has been built up over five years, since 2008. GCHQ set up a three-year trial at the GCHQ station in Bude, Cornwall. By the summer of 2011, GCHQ had probes attached to more than 200 internet links, each carrying data at 10 gigabits a second. "This is a massive amount of data!" as one internal slideshow put it. That summer, it brought NSA analysts into the Bude trials. In the autumn of 2011, it launched Tempora as a mainstream programme, shared with the Americans.

(6) Message content is maintained for three full days in what is referred to as an "internet buffer" ... Tempora allowed the agency to set up internet buffers so it could not simply watch the data live but also store it – for three days in the case of content and 30 days for metadata. "Internet buffers represent an exciting opportunity to get direct access to enormous amounts of GCHQ's special source data," one document explained. It also details a constant effort to build up storage capacity at the stations at Cheltenham, Bude and at one overseas location and ongoing technical work to expand GCHQ's capacity to ingest data from new super cables carrying data at 100 gigabits a second.

(7) Suggestions that GCHQ now captures more signals than the NSA.

(8) NSA's General Alexander made a casual remark supporting the breadth of GCHQ's internet interception capabilities, in particular Menwith Hill's role, and his awareness of the situation: Why can't we collect all the signals all the time? Sounds like a good summer project for Menwith. - General Alexander, Menwith Hill, June 2008.

(9) UK legal basis for interception "is in doubt" ... According to GCHQ's legal advice, it was given the go-ahead by applying old law to new technology. The 2000 Regulation of Investigatory Powers Act (Ripa) requires the tapping of defined targets to be authorised by a warrant signed by the home secretary or foreign secretary. However, an obscure clause allows the foreign secretary to sign a certificate for the interception of broad categories of material, as long as one end of the monitored communications is abroad. Also states that it would be impossible to list the total number of people targeted because "this would be an infinite list which we couldn't manage".

The challanges mentioned for the project are predictable ... political fallout, global internet routes shifting away from the UK/US, ingestion-time filtering, and ongoing technical challenges regarding interception of ever-greater amounts of data.