If you're looking for something secure, check out the BSD line of Unix for i386s. As for the tools needed to hack your own network, there are tons of hacking tools available on the 'net, but what stops you from using them on external networks once you've finished with yours? If you want to do an assessment of what's not secure on your network, there are very good professional packages dedicated purely to looking for vulnerabilities on a local network and they will also give a list of patches and workarounds for most of the known vulnerabilities to lock down your network.

I haven't heard of a specific OS with everything already prepacked for something like that, though I know there are tools available which are small, proprietary computers which can be purchased through selected retailers. If you are interested in taking a look at one of inquiring regarding the pricing of such tools (they're not cheap...), PM me and I can give you some contacts to get a hold of.

AJ