Never mind the rant, you have a point if I re-read my (incomplete) statements (was too obvious perhaps but nevertheless not true).
Basically, what I mean mhkwood, is that the firewall comes in first. I do not promote our brand or anything, that is not the issue, even, like your own, it is based on a Linux Kernel.
Of course we do handle security, but I had not idea I had to elaborate on those aspects here ;-)
With me, security comes 1st as well, but my point is still, start with the firewall, it is your first point of entry. Whatever gap is in there will compromise anything else behind it, no matter how secure you make it.
As mhkwood states, drop everything and open what you REALLY need, in a controlled and monitored way. Build in shutdown and alerts when attacks are detected.
When I asked 'don't trust your firewall .?!??! ' the same applies for any security measures. If you don't trust them, don't use them. So, alternatively, if you DO use them, you should trust them (or yourself).
My building is locked and so are the doors ;-) If the solution is out there, let us know it was helpful, so others can benefit from it as well..