Thousands of National Security Letters are sent annually, don‘t need a judge‘s signoff, and it‘s illegal to tell anyone you got one. What do they demand? Web browsing history, the IP addresses of everyone corresponded with, all online purchases, and more.

Ars Technica‘s David Kravets reports that the details of the secret letters have emerged thanks to court moves from an ISP reluctant to secretly surveil its users for the FBI.