Learning Java

Policy Files

Java 2 provides a simple mechanism for protecting your computer from evil programs like viruses. If you download a program from somewhere on the Internet, how can you prevent it from stealing information on your computer and sending it back out into the Internet? How can you prevent a malicious program from disabling your computer or erasing data on your disk? Most computing platforms have no answer for these questions.

Java 2 offers powerful ways to limit the actions of running code. Before Java 2, much of the buzz about security had to do with the security of applets. The applet ran with security restrictions that prevented the applet from doing questionable things like reading from or writing to the disk or contacting arbitrary computers on the network. In Java 2, it’s just as easy to apply applet-style security to applications. Furthermore, it’s easy to fine-tune the access you allow applications. For example, you can allow an application to access the disk, but only in a specific directory, or you can allow network access to certain addresses.

Why is this important? Let’s suppose that you need a certain application, like a calendar or an address manager. You go to your favorite Internet search engine and find a promising-looking Java application that does just what you want. You download and run it. But it’s entirely possible that what you’ve downloaded is not what you wanted. It could be a computer virus that infects your computer. Or it could simply be a malicious ...