Unable to Hook Ctrl+Alt+Delete

[Alexinuk]

Hi, I'm having a problem getting my hooks to work. I can successfully hook Keyboard and System messages (WH_KEYBOARD and WH_SYSMSGFILTER) but can't seem to be able to prevent Ctrl+Alt+Delete or MSGF_NEXTWINDOW from doing what they normally do. I'm trying to prevent users of my app from accessing windows (definately not what i'd want, i know, but clients are clients), and i've got a feeling that part of the problem is the differences between 95/98 and 2k/XP? any ideas? Thanks in advance to anyone who can help, Alex

[Joan M]

You'll never be able to hook that keystroke using a system wide hook or any other technique... In order to do that you must create a GINA.DLL that handles that keystroke as you want... Hope this helps...

[Alexinuk]

Joan Murt wrote: You'll never be able to hook that keystroke using a system wide hook or any other technique... In order to do that you must create a GINA.DLL that handles that keystroke as you want... I've been told this before - do you mean MSGINA.DLL? My version of Win98 doesn't have this dll present, but apparently WinNT does. does this matter? Have you got any idea where I can look to find out a few clues on how to do this? Cheers for the response, Alex

[xxhimanshu]

hi It is possible to hook Ctrl+Alt+Del combination by replacing the definition to Msgina.DLL in the registry by your own dll that is handling all the keyboard messages and forwarding all allowed key combinations to the original msgina.dll. The easiest way to prevent unauthorized process kills is to use the VC++ resource editor, open msgina.dll and by making all buttons in the task manager dialog box disabled except Cancel. This is not a very beautiful method, but it works... i saw an article on CP last days..search for it..it was on hooking ctrl + alt + del.. type something.. hope this works.. Himanshu

[HENDRIK R]

Win95 + 98 don't have a MSGINA.DLL. Hooking can be done by setting the screensaver state programatically. The call

SystemParametersInfo(SPI_SETSCREENSAVERRUNNING, TRUE, lpvoid, 0)

blocks the keys, and

SystemParametersInfo(SPI_SETSCREENSAVERRUNNING, FALSE, lpvoid, 0)

re-enables them. For replacing MSGINA.DLL you should search the MSDN. There're some good examples and explanations.

[Alexinuk]

Thanks for that. I'd figured out the screensaver bits but was unsure if that was the accepted way of doing it. Basically it sounds like such a muck-about to do all this that i'm probably going to try and get my boss to persuade the clients that they don't realy want this feature after all. If there were one way for all versions of Windows, then perhaps it would work, but I would also need to disable the Windows Key, Alt+Tab, Alt+Esc and Ctrl+Tab to actually prevent anyone using the app from accessing the desktop. All in all I'd never implement something like this through choice:(. Thanks for the support though! -Alex

[Alexinuk]

If I were to go a step further and prevent the Task Manager from even being shown, would I be able to write my own GINA.DLL (instead of changing microsoft's and just disabling buttons), and if so how easy is this to do and where would I start to look to do it? Thanks for the reply! -Alex