I've thought for a long time that this is a broader problem with the whole firewalls-and-NAT network security paradigm. It leads to a "soft underbelly problem"

I've thought for a long time that this is a broader problem with the whole firewalls-and-NAT network security paradigm. It leads to a "soft underbelly problem" and a complacency that leads to insecure internal systems. From what I've seen: God help most organizations if someone gets to the internal LAN! The rule should be: If your thing can't run securely on the unfiltered Internet, it's broken. Any firewalling and such should be a defense-in-depth afterthought. Of course this is kind of perfect world thinking. The reality is that quite a lot of software is either broken or insecure by design (e.g. databases that assume a secure LAN and don't even authenticate nodes) and so in practice we're quite far from this being practical for all but the most carefully managed deployments. Developers are also notoriously lazy about security while developing. I'm as guilty of this as the next dev sometimes.