Wired published an interesting article on Narus' deep packet-inspection technology said to be the basis of the NSA's internet surveillance:
"Narus' product, the Semantic Traffic Analyzer, is a software application that runs on standard IBM or Dell servers using the Linux operating system. It's renowned within certain circles for its ability to inspect traffic in real time on high-bandwidth pipes, identifying packets of interest as they race by at up to 10 gigabits per second.
Internet companies can install the analyzers at every entrance and exit point of their networks, at their "cores" or centers, or both. The analyzers communicate with centralized "logic servers" running specialized applications. The combination can keep track of, analyze and record nearly every form of internet communication, whether e-mail, instant message, video streams or VOIP phone calls that cross the network.
Brasil Telecom and several other Brazilian phone companies are using Narus products to charge each other for VOIP calls they send over one another's IP networks. Internet companies in China and the Middle East use them to block VOIP calls altogether."
