I have Mountain Lion (fresh install as of today), I have also reset the router and it has no port forwarding or anything. There are no other devices connect to the router but just the mac. I did a port scan on my IP and found that port 21 and 22 were open.
The type of router that I have is a ubee ddw3612. The ISP that I am using is Charter and true or not I heard something about if a person knows your mac address they can spoof their and use my mac address to connect to the internet for free.
That is the only conclusion I can come to with these ports open and I have tried everything to be very sure its not the computer or the router. What do you think?