03/05/2013 05:32 pm ET Updated May 05, 2013

Google Transparency Report Offers Details On National Security Letters

Google updated its Transparency Report on Tuesday with details about the the US government's use of national security letters, a controversial investigative technique that was greatly expanded after 9/11 under the Patriot Act.

The update revealed that between 1,000 and 1,999 of the internet search giant's users were affected by between 0 and 999 of the letters. The FBI and other agencies can issue those letters to demand basic identifying information on users without a warrant as part of national security investigations.

The transparency report numbers are purposefully vague. As Google noted in a blog post accompanying the update, the FBI and other agencies using the letters can impose a gag order on the ISPs, email providers and other companies who receive them.

One man who ran a small ISP, Nicholas Merrill, has fought for nine years to reveal more details about a national security letter he received, and fought, in 2004.

"The FBI has the authority to prohibit companies from talking about these requests," said Richard Salgado, legal director, law enforcement and information security at Google. "But we've been trying to find a way to provide more information about the NSLs we get -- particularly as people have voiced concerns about the increase in their use since 9/11."