Bruce Schneier has a very interesting post about the current state of internet monitoring, which would seem to be pretty total. He links to a Daily Kos piece, which states
Specifically, this equipment was the Narus ST-6400, a machine that was capable of monitoring over 622 Mbits/second in real time in May, 2000, and capturing anything that hits its’ semantic (i.e. the meaning of the content) triggers. The latest generation is called NarusInsight, capable of monitoring 10 billion bits of data per second.
I recommend reading the whole thing. It seems to have no direct purpose, it doesn’t break a single code, and it does absolutely nothing to discover anything about the use of steganography (messages in plain site). However it does seem like it would be useful to discover the terrorist (or whatever) networks (probably with a lot of false positives).
In any case, I think it’s safe to say we have no digital privacy anymore.