Missed calls, border crossings, credit card payment authorizations, geotagging, route planning and arranging meetings: Even our more banal SMS text messages can yield telling data, as the US National Security Agency (NSA) is reportedly well aware.

The Guardian newspaper and Britain's Channel 4 News jointly reported late on Thursday that the NSA had been gathering data on millions of SMS text messages per day, in an operation codenamed "Dishfire."

The report was based on a June 2011 NSA presentation, obtained via fugitive former NSA contractor Edward Snowden, with the subtitle: "SMS Text Messages: A Goldmine to Exploit." As published on the Guardian website, the NSA document appeared to claim that in April of 2011, the NSA scooped up an average of 194 million such messages per day.

"The NSA has made extensive use of its vast text message database to extract information on people's travel plans, contact books, financial transactions and more - including of individuals under no suspicion of illegal activity," the Guardian's James Ball wrote from New York.

Later on Friday, US President Barack Obama is scheduled to announce reforms to intelligence-gathering practices - effectively a result of the reports surfacing since Edward Snowden turned whistleblower last summer. His announcements follow a report from a special investigative panel, completed and handed to the president in December.

NSA: Neither arbitrary nor unconstrained

The NSA responded to the latest reports late on Thursday, primarily disputing the Guardian report's claim that the intelligence agency collected "pretty much everything it can."

"As we have previously stated, the implication that NSA's collection is arbitrary and unconstrained is false," the NSA statement said.

The NSA went on to say its activities "are focused and specifically deployed against - and only against - valid foreign intelligence targets in response to intelligence requirements."

While promising that, for US citizens, "privacy protections exist across the entire process concerning the use, handling, retention, and dissemination of SMS data," the NSA statement was less emphatic on the issue of foreign nationals' data.

"In addition, NSA actively works to remove extraneous data, to include that of innocent foreign citizens, as early as possible in the process," the statement said.

Opinions vary considerably on whether Barack Obama is likely to present meaningful changes to NSA policy on Friday. Critics like journalist and Snowden-confidant Glenn Greenwald have said they expect very little of substance, while a former intelligence agent warned DW that the changes could be so radical as to pose security threats for the US.

msh/jr (AFP, dpa, Reuters)