Comcast has done this on a large percentage (perhaps all) of their customers' equipment as a preventative measure. It's not because of anything you've done.

Being one of if not the largest ISP in the country, they get a lot of spammers using their service.

This is a good thing, IMO. Comcast will likely have to spend millions on support calls from confused customers, but I think they're doing the right thing. I don't agree with many of their practices, but I think this one's good.