This week's giveaway is in the EJB and other Java EE Technologies forum. We're giving away four copies of EJB 3 in Action and have Debu Panda, Reza Rahman, Ryan Cuprak, and Michael Remijan on-line! See this thread for details.
You will need to use the security manager; see the Security Features in Java SE tutorial to start with. This is how applets are prevented from accessing local files, and from using reflection to get around these limits.