The Guardian newspaper and Britain's Channel 4 News reported yesterday that the NSA used the messages to extract data on the location, contact networks and credit card details of mobile users.
British spies were given access by the NSA to search the collected "metadata" -- information about the text messages but not the actual contents -- of British citizens, according to the report.
There was no immediate reaction from the NSA.
The secret files say the programme, codenamed Dishfire, collects "pretty much everything it can", the Guardian and Channel 4 News reported. Dishfire works by collecting and analysing automated text messages such as missed call alerts or texts sent to inform users about international roaming charges, the news organisations said.
It was also able to work out phone users' credit card numbers using texts from banks. They cited an internal NSA presentation from 2011 on the programme and papers from Britain's electronic eavesdropping facility GCHQ.
There was no immediate reaction from the NSA. GCHQ said it worked within British law. "All of GCHQ's work is carried out in accordance with the strict legal and policy framework which ensures that our activities are authorised, necessary and proportionate and that there is rigorous oversight," it said in a statement.