mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-18 17:36:11 +00:00
342 lines
8.4 KiB
NASM
342 lines
8.4 KiB
NASM
.model tiny
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.code
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org 100h
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start:
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jmp short begin_code
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copyright db "HYBRiS.1435 Remover. (c) 1995 The Unforgiven/Immortal Riot",0
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begin_code:
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push dx ; Cool self-check..
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push ds
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mov ah,9
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mov dx,offset intro_msg
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int 21h
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pop bx
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pop dx
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cmp bx,dx
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jne wrong
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mov ah,9
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mov dx,offset ok_msg
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int 21h
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jmp short start_msg1
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wrong:
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mov ah,9
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mov dx,offset wrong_msg
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int 21h
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int 20h
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intro_msg db 'Selfcheck $'
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ok_msg db 'OK',13,10,'$'
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wrong_msg db 'Failed',13,10,'$'
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start_msg1:
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mov ah,9 ;print starting msg...
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mov dx, offset begin
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int 21h
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mov ah,0 ;did they agree on the rules?
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int 16h
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cmp ah,15h ;y/Y
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je ok_phile ;yes, they did
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mov ah,9 ;print blah..
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mov dx, offset not_yes
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int 21h
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int 20h
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not_yes db "User Failure!",13,10,07,36
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ok_phile:
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mov ah,4ah ;Do a virus installation check. . .
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mov bx,0ffffh
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mov cx,0d00dh
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int 21h
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cmp ax,cx ;ax=cx=d00d= the virus is TSR. . .
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jne not_res
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mov ah,9
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mov dx, offset resident
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int 21h
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int 20h
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not_res:
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mov ah,2fh ;Get DTA-area to es:bx
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int 21h
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mov ah,4eh ;find first file matching ds:dx (com)
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;with any attribute
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next:
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mov cx,7
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mov dx, offset f_com
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int 21h
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jc no_com ;we have no more com-files
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call main ;got a com-file - search it
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mov ah,4fh ;get next com-file
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jmp short next
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no_com:
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terminate: ;no more files!
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mov ah,9
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mov dx, offset stat1
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int 21h
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; This nice statistics is made by Blonde. Greetings to him.
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mov dx, word ptr [count]
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call dec16out
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mov ah,9
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mov dx, offset stat2
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int 21h
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mov dx, word ptr [inf]
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call dec16out
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mov ax,4cffh
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int 21h
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main:
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inc byte ptr [count]
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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 di
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push si
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push es
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push es
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pop ds
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push cs
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pop es
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mov si,bx
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add si,1Eh ;bx = pointer to fname (1eh)
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mov di,offset fname_buf
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mov cx,0Fh ;cx=15
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push cx ;save cx = 15
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push di ;save di (fname)
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rep movsb ;rep until cx=0
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pop di ;restore di
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pop cx ;and set cx=15
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xor al,al ;zero out al
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cld ;Clear direction
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repne scasb ;Scan es:[di] for al
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push di ;save di
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mov al,20h ;
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rep stosb ;Store al (fname) to es:[di]
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mov byte ptr es:[di],36 ;'$'
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pop di
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pop es
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push cs
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pop ds
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;mov ah,9 ;print fname
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;mov dx,offset fname_buf
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;int 21h
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mov cx,15 ;with BIOS function due to this procedure
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mov si, offset fname_buf ;can be used quite frequently. This is
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lup: lodsb ;faster
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int 29h ;mov ah,0ch, int 10h
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loop lup
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mov ax,3d02h ;prepare open in read/write access
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mov dx,bx ;bx into dx
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add dx,1eh ;bx = pointer to fname
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push es ;make es=ds
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pop ds
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int 21h ;do it!
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jnc read_file
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mov ah,9 ;uerm? we couldnt open the file
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mov dx, offset error_open ;fucking write-protected.. or lame coding
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int 21h ;not zoinking f_attribs??
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jmp no_inf
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read_file:
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mov bx,ax ;place file handle in bx
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mov ah,3fh ;read first 4 bytes of the file
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mov cx,4 ;to a buffer in memory
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mov dx, offset read_buf
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int 21h
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cmp byte ptr ds:[read_buf+3],'@' ;4th byte = @?
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jne No_inf
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cmp byte ptr ds:[read_buf],0e9h ;1st byte = jmp?
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jne no_inf
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inc byte ptr [inf]
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mov ah,9 ;say that the file is infected
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mov dx, offset is_inf
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int 21h
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mov ah,0 ;wait keypress
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int 16h
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cmp ah,15h ;y/Y ?
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je remove ; => they want to remove it..
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jmp no_inf
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remove:
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mov ax,4202h
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mov cx,-1
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mov dx,-4
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int 21h
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mov ah,3fh ;read those bytes to a buffer
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mov cx,4
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mov dx,offset read_buf
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int 21h
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mov ax,4200h ;seek the 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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mov ah,40h ;write the original bytes to
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mov dx,offset read_buf ;the top of file
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mov cx,4
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int 21h
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mov ax,4202h ;seek (filesize-vir_size)
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mov cx,-1
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mov dx,-1435
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int 21h
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mov ah,40h ;truncate vir_size..
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xor cx,cx
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int 21h
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mov ah,9 ;Report that the file is clean. . .
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mov dx, offset _clean
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int 21h
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mov byte ptr [clean_f],1
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no_inf:
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cmp byte ptr [clean_f],1
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je skip
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mov ah,9 ;say that the file is infected
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mov dx, offset is_cle
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int 21h
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skip:
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mov ah,9 ;print linefeed instead of
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mov dx, offset linefeed ;mov byte ptr es:[di-1],13
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int 21h ;mov byte ptr es:[di],10
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;mov byte ptr es:[di+1],36 (see above)
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;this is simpler for reporting. . .
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mov ah,3eh ;close file
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int 21h
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pop si ;restore registers in use
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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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ret ;and return to caller
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dec16out:
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push ds ;This convertation is
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push di ;Blonde(tm)
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push dx
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push cx
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push ax
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xor cx,cx ;initialize the counter
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lea di, buf ;point to a buffer
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dec16out1:
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push cx ;save the count
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mov ax,dx ;AX is the numerator
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xor dx,dx ;clear upper half
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mov cx,10 ;divisor of 10
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div cx ;divide
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xchg ax,dx ;get quotient
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add al,30h ;increase to ASCII
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mov [di],al ;put in byte in ascii-format
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inc di ;point to next byte
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pop cx ;restore count
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inc cx ;count the digit
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or dx,dx ;done? (dx=0?)
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jnz dec16out1 ;if not zero, loop until dx = 0
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dec16out2:
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dec di ;decreasment of di
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mov dl,[di]
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mov ah,2
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int 21h ;write dl to screen output
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loop dec16out2
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pop ax ;restore registers
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pop cx
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pop dx
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pop di
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pop ds
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ret ;and return
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begin:
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db "Remover for the HYBRIS virus: This program is free of charge for all users.",13,10
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db 'DISCLAIMER: This software is provided "AS IS" without warranty of any kind,',13,10
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db "either expressed or implied, including but not limited to the fitness for",13,10
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db "any particular purpose. The entire risc as to its quality of performance",13,10
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db "is assumed by the user. Agree with those rules [Y/N]",13,10,36
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f_com db "*.COM",0 ;COM-spec
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buf dw ?
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read_buf db ?,?,?,? ;4 buffers to read into
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is_inf db "Is infected! Remove it? [Y/N]$ "
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_clean db " File is now clean....$"
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is_cle db "is clean...$"
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error_open db " Error open file$ ";shouldnt happen. . .
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resident db "Virus is already resident, aborting$"
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fname_buf db 65 dup (?) ;fname = max 64, but ah well!
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linefeed db 0ah,0dh,'$' ;linefeed+ end of print marker.
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count dw 0
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inf dw 0
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clean_f db ?
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host_clean db "Self-checking OK!",13,10,36
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host_infected db "Program is infected and will not run$",13,10
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stat1 db 13,10
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db "Number of files scanned: $"
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stat2 db 13,10
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db "Number of files cleaned: $"
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end start
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================================================================================
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