Can somebody recommend
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I have a server that runs Ubuntu. I've noticed that somebody is constantly trying to access my pages for 'logged in' users without being logged in. Also there were several attempts to guess the address of phpmyadmin, etc.

I've been a web developer for a long time, so I know how to prevent SQL injections, etc. However, I'm not that confident about my server admin skills.

Can somebody recommend a good resource with the information about: 
1. How to make sure nobody gets SSH access to my server.
2. How to prevent somebody from getting access to my database.

Specifically, I'm looking for ways to whitelist IP addresses for both SSH and MySQL, so that only me can connect to my server over SSH and only my server can connect to my database. 