Ports are like the windows and doors to your house. The more ports you have open, the more ways there are to get into your house. Which is why it is important for companies to only have the ports that they need currently open. You also want to make sure that all ports that you have open, are monitoring the traffic that is coming over that port. Each port only accepts certain types of traffic, but protocols can be nested to look like a different protocol to gain access to your network. This is both a useful and dangerous feature of using Ports. Example: Mapi over RPC over HTTPS. This means that the Mapi Protocol is nested under the RPC protocol, which is nest under the HTTPS protocol. Which means that all these protocols can come in through the HTTPS Protocol Port, Port 443. This is useful, as you can accept more protocols, than ports you have open. Securing your network even further. It is dangerous, as hackers also know how to utilize this and can mask their entries into your network. So, you while you want to make sure that you can easily access your house, you also need to make sure that others are not able to do so, by limiting the open ports into your network.