I created a Raspberry Pi NAS with open media vault and piOS. I then attached a large hard drive and connected it to my router, and configured it to be able to connect with my laptop and phone locally and remotely. I even started playing around with some docker containers and created a rss reader and pihole/unbound to route my local traffic. I must admit I know very little about networking and was only able to accomplish this task by following how to post and help from the members out here. Furthermore, I even created my own dns with duckDNS.
The question is, since my pi and hard drives are now assessable on the internet, how do I make sure that my setup is secure? How do I confirm that my leaks or whatever are patched? How do I check if anyone has hacked in or installed any viruses or trackers (virus scan software?), or any other malicious things one might do?
Bottom line, how do I (a relative newbie) make sure that my setup is secure and private for just my use while still having it connected to the internet?