Is this some kind of Buffer Overflow?

Hi,
I have a LAN with Internet access for over 10 people, the Internet passes through my computer first (i act as a server or ISP for them), recently there's someone on the network who sends a LOT of requests to port 2869 on my computer, i searched and found that it's something to do with UPnP, actually i don't know a lot in Networking, but anyway, i don't have UPnP installed in the first place, so what's going on please?