Snort, the GPL'ed NIDS, has rules files for packet signatures to match, and there are Vim syntax files to appropriately colorize these snort rules files. They can be downloaded from <http://www.snort.org/Files/hog-vim.tar.gz>. It'd be nice if they were added to the vim RPMs
These were magically added sometime between beta2 and RC1. I'll close this bug.