Prevent C# app from process kill

How can I protect my C# app from someone killing its process via taskman or programmatically?

Here is my scenario:

App A is an MFC app developed by another team. It has an unpublished text-based remote interface that is enabled via a backdoor.

I'm developing app B, a C# WinForms app which interacts with A. B enables A's backdoor when it needs remote access closes it when finished (or on failure).

I'm exploring ways users could abuse B in order to gain access to A's hidden functionality, such as killing B's process after it has enabled A's remote interface. I'd like have one last chance for B to close A's backdoor when that happens.

B uses localhost to interact with A, so I'm not worried about the power-down scenario.

I'm looking for a solution that doesn't involve changing A.

I'm not expecting to be able to stop Dark Tangent (though that would be a bonus), but right now a script kiddie could have his way with this design :)

These apps run on Windows XP, but will also soon support Vista & 7.

Thanks in advance, Jim

Solution 1:

I'm willing shut the app down when they try but need to do some things first.

Having necessary steps at program shutdown leads to fragile programs that break easily. Even if you could prevent someone from killing your program via the task manager, you cannot stop them from turning off the computer, or even pulling the cable out of the wall. Whatever task that was so vitally important to complete will be lost. And what if there is a power cut? Again your task won't complete and your vital clean up code will not be run.

Instead you should make your program robust to failures at any point. Use transactions, and always save state to files atomically - make sure that you always have at least one valid copy of your data. Don't overwrite important files in a way that they become temporarily invalid.

Finally, you can add a dialog box to your program that when they try to close it, warns them that the program needs to shut down properly. If you make your shutdown fast users won't want to kill it and will let it terminate properly. If your shutdown takes ages then people will try to kill it. If you are nice to your users, they will be nice to you too.

If shutting down fast means that the user will lose some unfinished work then warn them about this and give them the opportunity to wait for the task to finish, but if they really want to quit your program then let them quit.

Solution 2:

You can't - as long as the user has the right to call TerminateProcess on your program, you can't prevent End Process from killing you immediately in task manager. Raymond Chen posted on this some time ago: The arms race between programs and users