Open ports are extremely important, especially for further control with a remote system. An open port is a clear sign of activity and broadcast on a target system, and having multiple ports open indicates several things. Firstly and mainly, it's generally not safe to have all ports open in terms of security. Some ports can be accessible through various network connections and be insecure for potential attacks coming out of the device environment, as we will show in the next pages.

If you read the previous chapter carefully, you probably have an idea of how easy it is to exploit a vulnerability in suitable conditions using a wide variety of scripts offered by the Nmap Scripting Engine (NSE). The point is, if you leave a port open and accessible, the device accepts anything that is sent to it, even malicious communication requests coming from attackers. Therefore, you could say that your primary goal to increased security would be to have all ports left closed, so the device does...