Some of the world's leading telecoms firms are secretly collaborating with Britain's spy agency GCHQ, passing on details of their customers' phone calls, e-mail messages and Facebook entries, documents leaked by the whistle-blower Edward Snowden show.
BT, Vodafone Cable and the US firm Verizon Business - together with four other, smaller providers - have given the Government Communications Headquarters secret, unlimited access to their network of undersea cables. The cables carry much of the world's telephone and internet traffic.
In June, details emerged of GCHQ's ambitious programmes aimed at scooping up as much online and telephone traffic as possible. It was revealed that GCHQ was able to tap into fibre-optic cables and store huge volumes of data for up to 30 days. That operation, code-named Tempora, has been running for 20 months.
On Friday Germany's Suddeutsche newspaper published the most highly sensitive aspect of that operation - the names of the commercial companies working secretly with GCHQ, and giving the agency access to their customers' private communications. The paper said it had seen a copy of an internal GCHQ PowerPoint presentation from 2009 discussing Tempora.
The document identified for the first time which telecoms companies are working with GCHQ's "special source" team. It gives top-secret code names for each firm. The companies refused to comment on any specifics relating to Tempora, but several noted they were obliged to comply with British and European Union law.
The revelations in June emerged at the same time as the Sunday Morning Post revealed that computers at the Hong Kong headquarters of Pacnet - owner of one of the biggest fibre-optic networks in the region - were hacked by US spies in 2009.
Pacnet, which has global headquarters in Hong Kong and Singapore, owns more than 36,800 kilometres of fibre-optic submarine cables and provides connections to 16 data centres for companies and governments across the Asia-Pacific region.