To prevent hacking keep following points in your mind:
-Keep your passwords secret.
-If you have to give your password to someone, make sure that you change it,after they have accessed it.
-Don't write down passwords or share them with too many people.
-Periodically change your passwords. You can find more tips by searching "How can I make a stronger password?"
-Make sure that your personal computer does not contain viruses, trojans, keyloggers, etc.
-Keep your scripts and downloaded programs updated. Always upgrade to the latest version of your blog, forum, shopping cart, etc.
-Do not have writable file permissions. The correct permissions are normally 755 or 644, and you can check these in your File Manager. Most users know to avoid 777 permissions, but you really should avoid any permission settings which allow group and world writing. (That's anything ending in 7, 6, 3, or 2. The first number can be one of these, but not either of the last two numbers.)