We've created a free tool for visualizing live streams of network traffic, using JMonkeyEngine (Java 3D gaming engine).
Please take a look at deepnode.com - we would very much appreciate feedback from this community.
Rather than focusing on mining of static datasets, this tool focuses on seeing activity over time, and controlling the timeline so that a human can connect the dots. Here's a link to information on the concept behind the visualization style.
As for the screenshot, this video explains what you're looking at.