#132947 - 2005-01-25 01:17 PM
Disabling the f8 key.
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Stephen Wintle
Seasoned Scripter
Registered: 2001-04-10
Posts: 444
Loc: England
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Hi,
I work in a school (with many naughty pupils) and I want to be able to take the ability away for pupils to be able to use the 'f8' key during bootup. I have searched and found a few referals to a ntldr file 'ntldrnof8', however this file seems to stop my machines booting up altogether. I use windows 2k clients can anybody help?
Regards
Steve.
_________________________
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#132950 - 2005-01-25 03:55 PM
Re: Disabling the f8 key.
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Sealeopard
KiX Master
Registered: 2001-04-25
Posts: 11164
Loc: Boston, MA, USA
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For those who love Assembler or are loving IT way to much, here's the solution:
Quote:
I got it! I needed the same thing, did some spelunking and found that ntldr does the F8 checking & displays the troubleshooting menu. Since ntldr is pretty small and can only use BIOS INT 16 for keyboard input, it was pretty easy to look amongst all the INT 16 (keyboard handler) byte sequences in there (there were only three). I found this one at offset 085A:
MOV AX,0100 INT 16 ;Checks if keystroke waiting in buffer, ZF=0 if yes, ZF=1 if no JNE 09 ;Jump ahead nine bytes if ZF=0
By just replacing the JNE 09 with three NOP's (no op, byte code 90), I disabled execution of the keyboard input handling, so no more response to F8 key press. If you want to check for yourself, load ntldr into your assembly editor and search for "CD 16" hex string. You'll find three; this one's the second.
If you don't want to fuss with doing yourself, I've put a copy of my ntldr on our ftp site at skykomish.lib.washington.edu in the "Public" folder with the name "ntldrNOF8" (log on as "anonymous"). In this version, I also replaced the "press f8 for troubleshooting" text (found at bottom of ntldr) with <space> characters so that users don't see the F8 prompt.
Mike Reynolds Univ of Washington
Source: http://groups-beta.google.com/group/microsoft.public.win2000.security/browse_thread/thread/4db76c0cf6d216be?hl=en&
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