Shields Up!! is software by Steve Gibson an American software engineer, security researcher, and IT security proponent best known for his program SpinRite, for hard drive recovery.
It checks your router, that connects to the internet, to see if it is possible to hack . Your router should not respond to these tests. “The universal Plug and Play (UPnP) is a set of networking protocols that permits networked devices,
such as personal computers, printers, Internet gateways, Wi-Fi access points and mobile devices to seamlessly discover each other’s presence on the network and establish functional network services for data sharing, communications, and entertainment.
UPnP is intended primarily for residential networks without enterprise-class devices. ” (From Wikipedia). Your UPnP should not be externally exposed to hackers across the internet. Just go to grc.com and run Shields Up!! to see if you are protected in stealth mode. It is perfectly safe, free and over 104 million shields have been tested.