The National Security Agency has tapped directly into communications links used by Google and Yahoo to move huge amounts of email and other user information among overseas data centres, the Washington Post reported on Wednesday (October 31).

The report, based on secret NSA documents leaked by former contractor Edward Snowden, appears to show the agency has used weak restrictions on its overseas activities to exploit major U.S. companies' data to a far greater extent than realised.

Previously reported programs included those that allowed easy searches of Google's, Yahoo's and other Internet giants' material based on court orders. But since the interception in the newly disclosed effort, code named MUSCULAR, occurs outside the United States, there is no oversight by the secret intelligence court.

Like other companies, Google and Yahoo constantly send data over leased and shared or exclusive international fibre-optic telecommunication lines as they synchronise information.

The newly disclosed program, operated jointly with the United Kingdom's Government Communications Headquarters, or GCHQ, amassed 181 million records in one recent 30-day span, according to one document reported by the Post. It could not be learned how much of that included material from U.S. residents, how the agency redacted data on them or how much of the information was retained.

Presented by Adam Justice