NSA's PRISM access to Skype keys and PSTN gateways let them reach out and touch calls worldwide.

A National Security Agency document published this week by the German news magazine Der Spiegel from the trove provided by former NSA contractor Edward Snowden shows that the agency had full access to voice, video, text messaging, and file sharing fromtargeted individuals over Microsofts Skype service. The access, mandated by a Foreign Intelligence Surveillance Court warrant, was part of the NSAs PRISM program and allowed sustained Skype collection in real time from specific users identified by their Skype user names.

The nature of the Skype data collection was spelled out in an NSA document dated August 2012 entitled Users Guide for PRISM Skype Collection. The document details how to task the capture of voice communications from Skype by NSAs NUCLEON system, which allows for text searches against captured voice communications. It also discusses how to find text chat and other data sent between clients in NSAs PINWALE digital network intelligence database.

The full capture of voice traffic began in February of 2011 for Skype in and Skype out callscalls between a Skype user and a land line or cellphone through a gateway to the public switched telephone network (PSTN), captured through warranted taps into Microsofts gateways. But in July of 2011, the NSA added the capability of capturing peer-to-peer Skype communicationsmeaning that the NSA gained the ability to capture peer-to-peer traffic and decrypt it using keys provided by Microsoft through the PRISM warrant request.

The NSA was then able to task any Skype traffic that passed over networks it monitored or by exploitation of a targeted users system. NSA receives Skype collection via prism when one of the peers is a (FISA Amendments Act Section 702) tasked target, the Skype collection guide stated. Because Skype has no central servers, the guide explained, for multiparty calls, Skype creates a mesh-network, where users are connected together through multiple peer-to-peer links. Instant Messages sent to this group of meshed participants can be routed through any participant. If any participant in a chat was monitored, the NSA could capture all of the IM traffic in the shared chat.

Initially, NSA analysts had to piece together voice communications between peers because they were carried over separate streams, but a service added by August of 2012 by the NSAs Cryptanalysis and Exploitation Services (CES) automatically stitched both audio streams of a conversation together. As of 2012, however, analysts still had to search for associated video from a call session to match it up with audio in a tool called the Digital Network Intelligence Presenter (DNIP).

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Newly published NSA documents show agency could grab all Skype traffic