My mom doesn't like the idea of a NAS because It will need to be connected to the WiFi router and she thinks that it will be easily available to the internet and that files will be deleted/stolen. Anyway I can convince she's mostly wrong and that it will be a good idea?
If this doesn't go here can someone move this.
I really don't know all that much about it as I've never looked into it enough but I do know that if you use Synology to run your NAS, theres an Autoblock option that will block the IP address after a certain number of failed login attempts. Even if they try multiple ways to access the NAS, the IP address being the same will still be blocked so if they try and use SSH and then FTP login for example, it counts as two failed attempts and they'll be blocked. It could be set up with HTTPS as well if you want it to be secure while you're interacting with it, all SSL encrypted as well.
Just two basic things and I'm sure there are more. I'm sure you could also disable remote access if you never wanted it for that at all, just using it as a Local NAS only. Hopefully helps but that's about all I really know. Let me know how you get along!
TBH your NAS is probably less prone to viruses/hacks that your standard windows pc. I'm going to make a blanket statement and say that no NAS software is going to expose you files willingly to the internet by default. If you want files to be accessible outside of your home network, you will have to setup that up manually in whatever software you decide to use, with logins, and forward the ports on your router, etc. Your mom has nothing to worry about, in fact putting your files on a NAS with a raid would probably be safer as you can protect against hard drive failure as well.
On my Lenovo NAS there is an option to turn off remote administration so ssh and the likes are not reachable. I don't know if that makes it less prone to attacks but i haven't had any issues so far.