The NSA and TOR

TOR (a/k/a The Onion Router) is an anonymous, encrypted web browser bundle that, in theory, is intended to allow for untraceable activity in cyberspace.  Like most tools, it is neutral in value, and thus capable of use for good (it enables journalists to speak with sources and dissidents to communicate without scrutiny by authoritarian governments) and ill (it is widely used by criminals and, some say, by terrorists as well).  Until recently it was thought to be completely impervious to attack -- but recent disclosures suggest that the NSA has been working on the "TOR problem" for a while.  The Washington Post has the story:

[T]he NSA has mounted increasingly successful attacks to unmask the identities and locations of users of Tor. In some cases, the agency has succeeded in blocking access to the anonymous network, diverting Tor users to insecure channels. In others, it has been able to “stain” anonymous traffic as it enters the Tor network, enabling the NSA to identify users as it exits.

There are links to plenty of supporting documents and detail.  As always, those who are prohibited by their employment from reviwing classified material that was disclosed by Edward Snowden should refrain from clicking on the underlying links.