I have a server which listens on port 80 for incoming requests - using HttpListener. I've found that to be able to do that, I need to open up the port (add a firewall rule which enables me to listen on port 80). I've also made a method for removing this rule again, but if someone asks me why that's a good idea, I don't really know how I should answer. I think it's a good idea to clean up after your software's done with whatever it's doing, but is there some kind of security aspect to this or something that I'm missing?
Why is it a good idea to remove the firewall rule again after application exit?