Is that a pig I see flying? No, but VRT has released a a near real-time extension to snort.
I'm far from the first to discuss it, but figured I had to mention it because so much of the content on this blog has been, and will be, about near real-time network analysis.
My initial reaction is that I thought the day would never come. It was not too long ago that near real-time IDS was the domain of a few hardcore net defenders who built their own tools. Having built a platform for NRT and seen it used with great success, I can't advocate the technique zealously enough.
I'm really happy to see Sourcefire making this step toward the paradigm for which a few of us have been clamoring for years. Regardless of the implementation, just recognizing the validity of the paradigm and its value is an important step. Furthermore, the definition of NRT that VRT is using is very similar to the definition I've been using with my colleagues for some time. There seems to be a true understanding of what is being asked for, not just buzzword reflection.
While I haven't been able to play with it as much as I'd like, I have a few quick comments/thoughts:
If you have problems with libtool during compilation, delete the ltmain.sh from the unpacked tarball and replace it with the ltmain.sh from your distro's ltmain.sh. This file should be in the libtool package (rpm -ql libtool).
Other than that little issue, the install was easy for me.
The documentation is basically non-existent. Browsing through the source code, I got a bit of feel for what was going on, but I don't understand fully how everything fits together. A howto guide, explaining how to do NRT on arbitrary data would be nice, but who am I to complain about poor documentation :)
One thing that I was surprised to see, however, was an implementation of the pdf parsing routines in C. They utilized other C code written by Didier Stevens, but they didn't use his python implementation of what I think is similar functionality. I believe making use of existing code, with the smallest amount of re-factoring possible, is an important enabler for agility in NRT analysis. After all, in my view, NRT is about taking the detection tools used in other domains and applying them to data extracted passively from the network.
From what I can see, snort-nrt looks very promising.