#name: win xp sp2 PEB ISbeingdebugged shellcode

#Author: Teo Manojlovic

#Contact: teo.manojlovic@skole.hr

#Date: 14.12.2009.

here is the ASM code made using masm32

if program is being run under debugger the shellcode wil start beeping :D
//////////////////////begin///////////////////////////////////////

.386
.model flat, stdcall
option casemap :none
INCLUDE  C:\MASM32\INCLUDE\WINDOWS.INC
INCLUDE  C:\MASM32\INCLUDE\KERNEL32.INC
INCLUDE  C:\MASM32\INCLUDE\USER32.INC
INCLUDE  C:\MASM32\INCLUDE\MASM32.INC
INCLUDELIB  C:\MASM32\LIB\KERNEL32.LIB
INCLUDELIB  C:\MASM32\LIB\USER32.LIB
INCLUDELIB  C:\MASM32\LIB\MASM32.LIB

    .data
ExitMsg  DB "Enter to Exit", 0

  .code
 start:
assume fs:nothing
mov eax,fs:[30h]
mov     eax, [eax+02h]
mov ebx, 7FFF8000h
add ebx,7FFF8000h
inc ebx
push 300h
push 200h
mov edx,7c837a8fh
cmp eax,ebx
jnz exit
call edx
exit:
invoke ExitProcess,NULL

end start

/////////////////////////////end///////////////////////////////

here is the dump of code using olly debugger

00401000 >/$ 64:A1 30000000 MOV EAX,DWORD PTR FS:[30]
00401006  |. 8B40 02        MOV EAX,DWORD PTR DS:[EAX+2]
00401009  |. BB 0080FF7F    MOV EBX,7FFF8000
0040100E  |. 81C3 0080FF7F  ADD EBX,7FFF8000
00401014  |. 43             INC EBX
00401015  |. 68 00030000    PUSH 300                                 ; /Duration = 768. ms
0040101A  |. 68 00020000    PUSH 200                                 ; |Frequency = 200 (512.)
0040101F  |. BA 8F7A837C    MOV EDX,kernel32.Beep                    ; |
00401024  |. 3BC3           CMP EAX,EBX                              ; |
00401026  |. 75 02          JNZ SHORT antidebu.0040102A              ; |
00401028  |. FFD2           CALL EDX                                 ; \Beep
0040102A  |> 6A 00          PUSH 0                                   ; /ExitCode = 0
0040102C  \. E8 01000000    CALL <JMP.&kernel32.ExitProcess>         ; \ExitProcess
00401031     CC             INT3
00401032   .-FF25 00204000  JMP DWORD PTR DS:[<&kernel32.ExitProcess>;  kernel32.ExitProcess

here is the shellcode
\x64\xA1\x30\x00\x00\x00\x8B\x40\x02\xBB\x00\x80\xFF\x7F\x81\xC3\x00\x80\xFF\x7F\x43\x68\x00\x03\x00\x00\x68\x00\x02\x00\x00\xBA\x8F\x7A\x83\x7C\x3B\xC3\x75\x02\xFF\xD2\x6A\x00\xE8\x01\x00\x00\x00\xCC\xFF\x25\x00\x20\x40\x00