I recently had a conversation with someone on the Yahoo Customer Service Help Desk after I had a problem with my email account. During the conversation the following 'facts' were announced by this person:
1) NAT Routers and Firewalls are there to block viruses from getting onto the private network. They do not offer any protection against hackers getting passed them.
2) My network had been hacked. [Kaspersky Internet Security and Malwarebytes, both with the latest signature files, reported no infections on the computer]. When I told him this he said, no the hack is on your network not on the actual computer.
I actually have two cascaded NAT routers as the first one provides a guest network for visitors and the second router protects my own computers from any guest activity. Neither router has DMZ or any port forwarding enabled,