javasnoop

Normally, without access to the original source code, testing the security of a Java client is unpredictable at best and unrealistic at worst. With access the original source, you can run a simple Java program and attach a debugger to it remotely, stepping through code and changing variables where needed. Doing the same with an applet is a little bit more difficult. JavaSnoop attempts to solve this problem by allowing you attach to an existing process (like a debugger) and instantly begin tampering with method calls, run custom code, or just watch what’s happening on the system.

Only use this tool against systems you own or are explicitly authorized to test — see the disclaimer.