It can "reassemble" packets to show exactly what a user saw on their screen during a browsing session. HTTP Tracking:
Sources for this article include leaked documents from Edward Snowden, analysis by security experts including Bruce Schneier and Robert Graham, reporting by The Intercept, NDR, and WDR, and the published code snippets from the XKEYSCORE system.
What I saw was a function that relied heavily on heuristics. It checked language. It checked time zones. It checked character sets. But the code included a bypass flag.
The XKeyscore source code reveals several key features and capabilities that make the program so powerful: xkeyscore source code exclusive
: The NSA tracks all connections to Tor "directory servers" and "bridges," which are used to bypass censorship. "Extremist" Labeling
This rule triggers when a user visits the official Tor Project website — the user is connecting from a Five Eyes nation (US, UK, Canada, Australia, New Zealand). According to the document, simply searching the web for the Linux Journal or privacy tools could cause the NSA to mark the IP address of the person doing the search.
At the core of XKEYSCORE is its ability to reconstruct fragmented internet traffic into readable human activity. The source code highlights advanced Deep Packet Inspection (DPI) routines written primarily in C++ for execution speed, wrapped in Python scripts for configuration and extensibility. Protocol Extensibility It can "reassemble" packets to show exactly what
, which the system internally categorized as an "extremist forum". Training Slides (2013): Edward Snowden leaked dozens of slides through The Guardian Capability:
Look into the that resulted from these surveillance revelations. Share public link
analyzed fragments of the XKeyscore source code, identifying several specific behaviors that trigger surveillance: Privacy Software Interest : Users searching for privacy tools like are automatically flagged. Tor Network Use It checked language
Security experts praised the leak for its technical value. However, some quickly questioned its authenticity. Robert Graham of Errata Security noted: "The signatures are old (2011 to 2012), so it fits within the Snowden timeframe, and is unlikely to be a recent leak". However, he also found the code "weird, as if they are snippets combined from training manuals rather than operational code". This led to the consensus that the xkeyscorerules100.txt file likely originated from Snowden's documents but was an extract from a training presentation, not a live system dump.
The source code contains highly specific plugins designed to recognize the unique digital signatures of web applications. The system uses these parsers to automatically rip user credentials, chat logs, buddy lists, and geolocation data from unencrypted or poorly encrypted traffic. If a target logs into an unencrypted forum or uses an outdated mobile application, XKEYSCORE isolates the username and session token instantly. 2. Identifying Privacy Seekers