On Wednesday, the Guardian published a secret court order requiring Verizon to hand over data for all the calls made on its network on an “ongoing, daily basis.” Other revelations about surveillance of phone and digital communications have followed.

That the National Security Agency has engaged in such activity isn’t entirely new: Since 9/11, we've learned about large-scale surveillance by the spy agency from a patchwork of official statements, classified documents, and anonymously sourced news stories.

For more on surveillance, check out our roundup of investigative reporting on the issue and our rundown of how the government can get your digital data without a warrant.