Senator Asks Cellphone Carriers: What Exactly Do You Share With Government? Last year, Edward J. Markey, then a member of the House of Representatives, asked the country's major cellphone carriers to disclose how many data requests they received from federal and local law enforcement agencies. More than one million in 2011 alone, they said, revealing for the first time how ubiquitous cellphone records had become in criminal investigations. Now a member of the Senate, Mr. Markey is asking for this year's numbers and with more details. What exactly does the government seek from the carriers, he wants to know. How often do they ask for cellphone tower dumps, location data, content of text messages, browsing history and so on. How many of those requests did the companies comply with and how many did they deny and why? The letter to eight companies, including the largest carriers, AT&T, T-Mobile, and Verizon, was sent Thursday. It comes against the backdrop of mounting revelations about secret surveillance of Americans communications. Senator Markey's original request last year documented the fast-growing business of cellphone surveillance. Law enforcement sought a variety of records of cellphone subscribers in the course of routine street crime investigations, emergencies and counter-terrorism operations. At the time, carriers said they generally sought a search warrant or court order to comply with an law enforcement agency's request for data. But on certain categories of information, like location data, the law remains vague on whether a search warrant is required. This time around, in his letter, Senator Markey also sought to know how many times federal officials invoked Sec. 215 of the Patriot Act, which carries a gag order prohibiting recipients to discuss its details.