In general, applets loaded over the net are prevented from reading and writing files on the client file system, and from making network connections except to the originating host.

In addition, applets loaded over the net are prevented from starting other programs on the client. Applets loaded over the net are also not allowed to load libraries, or to define native method calls. If an applet could define native method calls, that would give the applet direct access to the underlying computer.