A fantastic successor to screen. tmux is small, easy to use and fast. It has a clear man file and is easy to compile. I've moved away from screen to tmux!
A Required Apache Module
I'm using this on a number of sites and I recommend anyone else worried about security do the same.
It's got an easy to understand configuration file, it's easy to install and it works exactly as advertised. I've seen a number of hack attempts blocked by this module. I'm running a number of PostNuke sites and I feel more at ease doing so, knowing that a number of the usual exploits of these sites can be blocked with the use of modsecurity.
The author is also very fast to respond to any requests for help and offered me great advice and help with the inital problems I faced (Not reading the manually properly...)