The Java platform has a number of built-in permissions that are used to control access to system resources. For example:

grant signedBy "Brad", codeBase "http://www.bradrubin.com" {
       permission java.io.FilePermission "/tmp/abc", "read";
};

allows code signed by "Brad" and loaded from "http://www.bradrubin.com" to read the /tmp/abc directory. See Resources for a complete listing of Java permissions.