NAT Problems

[Ragster2448]

I'm playing an online game, and when I join a match, it sometimes tells me to switch my NAT from strict to moderate or open so that I can easily join a match.

I know how to DISABLE my NAT, but I don't know how to turn it to moderate like it says. I don't want to risk getting a virus infection with disabled NAT, but I don't want a hard time trying to join matches. Is there a way to set it in-between enabled and disabled? Or should I just leave it alone and deal with the bad online play?