I mistakenly left this out of my Leopard security in 2012 post so rather than revise it and hope people read it again I will make a new post about a great security utility for OS X 10.5 Leopard. We all know what Little Snitch is right? It's a utility to block any outgoing connections you choose. They are at ver. 3 now and it does not support PowerPC as it requires Snow Leopard and up.
Not only is TCPBlock just as capable but it's free (donationware) and never gets in your face like Little Snitch loves to do. With it enabled along with the white list (safe apps/OS tasks) Leopard is even more secure. Any little things that won't work like file and screen sharing once this is enabled can be seen as blocked in the 'Connecting Apps' tab then selected followed by clicking the 'Insert into Application List' button. This is the easiest way to authorize underlying technologies like this that don't necessarily have attached applications.
Not only is this great for privacy but it allows you to learn what apps do call home and use DRM. I have been using this for around a year and can't imagine a Leopard install without it. It installs as a preference pane and also comes with an uninstaller just in case you decide against using it.
If you find it as useful as I do then you should consider a donation to the developer for creating such a great utility. Now go enjoy a more locked down (in a good way) Leopard.
PPC / Intel, Mac OS X 10.5 or later