Information
Changing the port used by MongoDB makes it harder for attackers to find the database and target it.
Rationale:
Standard ports are used in automated attacks and by attackers to verify which applications are running on a server.
Solution
Change the port for MongoDB server to a number other than 27017.
Impact:
Hackers frequently scan IP addresses for commonly used ports, so it's not uncommon to use a different port to "fly under the radar". This is just to avoid detection, other than that there is no added safety by using a different port.