I have minecraft downloaded onto my playstation 3 and it is accessible to all users. I'd like for my little brother not to be able to play it so is their anyway I can lock it for all users with a passcode or something?
Any way to lock certain games on my ps3?
From your PS3's XMB go to Settings > Security Settings!
Select [Change Password]. Follow the on-screen instructions to set the password. The password is set to [0000] by default at the time of purchase. Change the password and set your resrictions to prevent your brother from playing your minecraft
Just make sure you remember the password!
The Security Settings Password only works for certain things, see here:
http://manuals.playstation.net/document/en/ps3/current/settings/security.html#1080
So it won't prevent him from playing if the game isn't age restricted or parental controls aren't setup. So that's what you'll have to look into. If the account your little brother is on is set with an age of 18+, then it won't work at all. Without knowing if your brother is on a sub account or master account, that's all there's to it.