My router is a Frontier Comms DSL modem/wireless combo, on which UPnP has always been disabled, and the only open inbound ports are for ping (which my ISP uses to diagnose problems so I don't mind that).
"Stealth mode" was not enabled, but I've now enabled it. Normally if a router is contacted on a closed port, it responds saying it's closed. Stealth mode changes that response behavior to silence -- it appears as if the router doesn't exist.
FWIW, enabling stealth mode shouldn't make any functional difference other than you might disappoint the random scans done by the hackers and spammers.
Mine is one of the Netgears that looks like a stealth fighter jet, with antennas.
I have no idea what I’m doing.
:)