Which cell phone carriers are protecting privacy?

The office of Senator Ed Markey (D-Mass.) recently published letters from seven major cell phone carriers that replied to his request for information on how often they received and complied with law enforcement requests for customer data in 2012. The letters confirm what a similar inquiry from Sen. Markey revealed last year: law enforcement requests for customer data are growing in number and are less reliant on court approval.

This year's replies from cell carriers, however, contain significantly more information about each company's disparate privacy and storage policies. Pieced together, the letters provide a comparison of how long carriers will store customer information and under what circumstances they will hand over that information to law enforcement.

Privacy advocates have been unable to get precise figures on how often law enforcement agencies demand cell phone data, since the Freedom of Information Act (FOIA) does not apply to private companies. The American Civil Liberties Union (ACLU) has tried to create a snapshot of cell data collection by filing FOIA requests with law enforcement agencies across the country. In order to come up with the figures Sen. Markey obtained using the authority of his office, these organizations would have to file FOIA inquiries with every law enforcement agency in the nation.

Kade Crockford, a privacy blogger for the ACLU of Massachusetts, compiled a pair of charts comparing the information released to Sen. Markey from major cell phone carriers. The first chart demonstrates how long each carrier stores various pieces of customer data, such as call detail records (CDRs) and geolocation data.