By Dustin Volz
WASHINGTON (Reuters) - Microsoft Corp said on Thursday it had received at least a thousand surveillance requests from the U.S. government that sought user content for foreign intelligence purposes during the first half of 2016.
The amount, shared in Microsoft's biannual transparency report, was more than double what the company said it received under the Foreign Intelligence Surveillance Act (FISA) during the preceding six-month interval, and was the highest the company has listed since 2011, when it began tracking such government surveillance orders.
The scope of spying authority granted to U.S. intelligence agencies under FISA has come under renewed scrutiny in recent weeks, sparked in part by evolving, unsubstantiated assertions from President Donald Trump and other Republicans that the Obama White House improperly spied on Trump and his associates.
Microsoft said it received between 1,000 and 1,499 FISA orders for user content between January and June of 2016, compared to between 0 and 499 during both January-June 2015 as well as the second half of 2015.
The number of user accounts impacted by FISA orders fell during the same period, however, from between 17,500 and 17,999 to between 12,000 and 12,499, according to the report.
The U.S. government only allows companies to report the volume of FISA requests in wide bands rather than specific numbers.
FISA orders, which are approved by judges who sit on the Foreign Intelligence Surveillance Court, are tightly guarded national security secrets. Even the existence of a specific FISA order is rarely disclosed publicly.
The Washington Post reported on Tuesday that the FBI obtained a FISA order to monitor the communications of former Trump advisor Carter Page as part of an investigation into possible links between Russia and Trump's presidential campaign.
Parts of FISA will expire at the end of the year, unless U.S. lawmakers vote to reauthorize it. Privacy advocates in Congress have been working to attach new transparency and oversight reforms to any FISA legislation, and to limit government searches of American data that is incidentally collected during foreign surveillance operations.
Microsoft also for the first time published a national security letter, a type of warrantless surveillance order used by the FBI.
Other technology companies, including Twitter Inc and Yahoo Inc , have also disclosed national security letters in recent months under a transparency measure of the USA Freedom Act that was enacted into law by the U.S. Congress in 2015.
(Reporting by Dustin Volz; Editing by Bernadette Baum)