Re: ufw logging some blocked accesses - why?
Routers will automatically forward ports if your computer requests it. This is done through a system called Avahi, Bonjour, or UPnP. (maybe it has yet another name!)
If you are torrenting, you might have UPnP turned on in your Bittorrent program. Otherwise it might be an online game or something else that has activated UPnP.
If you want to turn it off completely, turn off UPnP in your router.
I try to treat the cause, not the symptom. I avoid the terminal in instructions, unless it's easier or necessary. My instructions will work within the Ubuntu system, instead of breaking or subverting it. Those are the three guarantees to the helpee.