The Bandit and Leviathan wargames on overthewire.org are fun newbie challenges to help get you started on security games. Though these go more into Linux fundamentals than they do actual security topics, they still are a good place to start. Playing these will help teach you a few things, but the most valuable lesson it gives is the importance of figuring things out on your own. The player is pushed to research commands via the man pages.

Bandit is the first in the sequence of games on the website. It holds your hand pretty well, and offers tips for what commands will be useful. It’s somewhat lengthy and has a good variety of things to do. Leviathan comes next, and though it doesn’t offer any hints at all, it is much shorter. After finishing Bandit, you should zoom through Leviathan pretty quickly. The only possible hangup is a beginner may have trouble if they aren’t familiar with ltrace or strace. That’s the only hint I’ll give though.

If you want to learn more about Linux or computer security, and don’t have any experience, then these are highly recommended.