What Can an Applet Do?

• Draw pictures on a web page
• Create a new window and draw in it.
• Play sounds.
• Receive input from the user through the keyboard or the mouse.
• Make a network connection to the server from which it came and can send to and receive arbitrary data from that server.

• Write data on any of the host's disks.
• Read any data from the host's disks without the user's permission. In some environments, notably Netscape, an applet cannot read data from the user's disks even with permission.
• Delete files
• Read from or write to arbitrary blocks of memory, even on a non-memory-protected operating system like the MacOS. All memory access is strictly controlled.
• Make a network connection to a host on the Internet other than the one from which it was downloaded.
• Call the native API directly (though Java API calls may eventually lead back to native API calls).
• Introduce a virus or trojan horse into the host system.
• An applet is not supposed to be able to crash the host system. However in practice Java isn't quite stable enough to make this claim yet.