[Samba] Problem with SAMBA

[Rodrigo Haces]

Hi, i have a debian box connected to internet by ADSL, in that box i share
internet to all my local network, i also have to share 3 directories with
samba with full read/write permissions.

my hosts.deny is ALL:ALL and my hosts.allow is ALL:127. AND ALL:192.168.0.
so that i only accept connections from inside my local network.

Here is the problem, i cannot ask for a password to let them write in my
directories because im using them as a database location so that my CRM
application connects there, but with this, intruders from outside my network
can write virus programs (And are actually doing it, writing a Xi.exe
program). So, how can i prevent this? here is my smb.conf:

[global]
        log file = /var/log/samba/log.%m
        passwd chat = *Enter\snew\sUNIX\spassword:* %n\n
*Retype\snew\sUNIX\spassword:* %n\n
        socket options = TCP_NODELAY
        obey pam restrictions = yes
        null passwords = yes
        encrypt passwords = true
        passdb backend = tdbsam guest
        passwd program = /usr/bin/passwd %u
        dns proxy = no
        netbios name = Servidor
        server string = %h server (Samba %v)
        invalid users = root
        workgroup = infosys
        debug level = 0
        os level = 20
        syslog = 0
        security = share
        panic action = /usr/share/samba/panic-action %d
        max log size = 1000

[bitacora]
       writeable = yes
       public = yes
       path = /files/bitacora


[comun]
       writeable = yes
       public = yes
       path = /files/comun

[admivi]
        writeable = yes
        public = yes
        path = /files/admivi

Thank in advanced
Rodrigo