No, it would be straightforward for a worm to figure out what internal network addresses they were using, what routers there were behind, and send packets to those routers whose destinations were those internal network addresses (192.168.1.2 or whatever). NAT does nothing to stop that.
Most routers won't forward those packets. But that's got nothing to do with whether those routers are running NAT or not.
Most routers won't forward those packets. But that's got nothing to do with whether those routers are running NAT or not.