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| OllyDbg IsDebuggerPresent Detection |
Debugging |
ap0x |
hidedebugger-IsDebuggerPresent.zip |
March 11 2006 |
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.386
.model flat, stdcall
option casemap :none ; case sensitive
include \masm32\include\windows.inc
include \masm32\include\user32.inc
include \masm32\include\kernel32.inc
includelib \masm32\lib\user32.lib
includelib \masm32\lib\kernel32.lib
.data
DbgNotFoundTitle db "Debugger status:",0h
DbgFoundTitle db "Debugger status:",0h
DbgNotFoundText db "Debugger not found!",0h
DbgFoundText db "Debugger found!",0h
.code
start:
; MASM32 antiOllyDBG example
; coded by ap0x
; Reversing Labs: http://ap0x.headcoders.net
; This example can detect all OllyDBG plugins that hook IsDebuggerPresent
; API. How? It gets PEB!BeingDebugged byte and stores 0x90 byte there.
; Then IsDebuggerPresent is called. If it returns value different from 0x90
; IsDebuggerPresent is hooked!
ASSUME FS:NOTHING
MOV EAX,DWORD PTR FS:[30h]
LEA EAX,BYTE PTR DS:[EAX+2h]
MOV BYTE PTR[EAX],90h
CALL IsDebuggerPresent
CMP EAX,90h
JNE @DebuggerDetected
PUSH 40h
PUSH offset DbgNotFoundTitle
PUSH offset DbgNotFoundText
PUSH 0
CALL MessageBox
JMP @exit
@DebuggerDetected:
PUSH 30h
PUSH offset DbgFoundTitle
PUSH offset DbgFoundText
PUSH 0
CALL MessageBox
@exit:
PUSH 0
CALL ExitProcess
end start
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