AT&T said Tuesday that a secretive US court ordered data turned over from more than 35,000 customers in six months as the telecom giant released its first "transparency report."
AT&T joined other telecom and Internet firms in releasing broad ranges of numbers following an agreement with authorities aimed at providing the public with more information on US data collection for national security investigations.
The transparency report, covering the first six months of 2013, said AT&T received between zero and 999 requests for customer content under the Foreign Intelligence Surveillance Act affecting between 35,000 and 35,999 accounts.
Under a separate listing, it said "non-content" data, which could be merely the user's identity, affected between zero and 999 accounts.
The company also received between 2,000 and 2,999 "national security letters"—which are generally FBI requests in terrorism investigations without a court order—affecting between 4,000 and 4,999 accounts.
"We take our responsibility to protect your information and privacy very seriously, and we pledge to continue to do so to the fullest extent possible and always in compliance with the law of the country where the relevant service is provided," AT&T said in a statement with the report.
"Like all companies, we must provide information to government and law enforcement agencies to comply with court orders, subpoenas, lawful discovery requests and other legal requirements. We ensure that these requests are valid and that our responses comply with the law and our own policies."
US authorities, facing legal challenges and a public campaign for more transparency, agreed last month to allow some information on national security requests but only in broad ranges, and with a six-month delay.
The deal came in response to pressure from the tech sector following leaked National Security Agency documents outlining vast surveillance of online and phone communications.
AT&T also said it received 301,816 requests from US law enforcement in civil and criminal investigations. It rejected the requests in 3,756 cases and provided only partial data in 13,707 other cases.
Explore further: FCC head seeks to narrow 'digital divide' with new proposal