This might have its uses, but it's risky to alert the person that you know they're there. They have a nasty habit of panicking and removing all logs via the "brute force method" - rm -rf *
For quick security solutions, I find Psionic's freeware products to be excellent utilities for security; they're not perfect, but if you need something fast and accurate, they'll do the job. Even if they are written in Python...
I think especially highly of PortSentry and HostSentry, although HostSentry takes a little longer to set up than PortSentry.
- email Ozymandias