Steve,
Is very important to block any TCP traffic that come with the
established flag off. This is very important for example if you have
intranets to protect, in this case for example, you want to allow
internal users to access web servers outside, but you don´t want outside
users access your intranet web, ftp, etc. Doing this you have to take
some ftp things to consider, you may need to use FTP passive connections
for your internal users access ftp servers outside.
Look, if you want more information you may get Building Internet
Firewalls (O'Reilly & Associates) at
www.greatcircle.com.
Hope this help.
Jaime A Botello C
Departamento de Redes y Telecomunicaciones
Información Selectiva S.A. de C.V.
Calzada San Pedro #507
Colonia Fuentes del Valle, C.P. 66220
Tel: (528) 318-8943
Fax: (528) 318-8981
email: jbotello @
infosel .
com .
mx
>
>
>-----Original Message-----
>From: Ricardo Alvarado [SMTP:ralvarado @
avantel .
com .
mx]
>Sent: Viernes 3 de Enero de 1997 9:21 AM
>To: firewalls @
GreatCircle .
COM
>Subject: Re: internal filtering router - filter config?
>
>>What type of things would you filter on the internal router? or even
>>the external router? I am going to be installing a firewall real soon
>>and would really appreciate any help.
>>
>>-steve.
>>matkoski @
dreamscape .
com
>
>In your external router you'd block any ICMP traffic going back and
>forth, as well as any packets bearing one of your internal IP
>addresses,
>as a source address, especially if these are going INTO your protected
>network. Also, kill telnets, fingers, snmp and snmp trap. Actually,
>kill
>any ports that your users will not be using, andl leave just mail, web,
>ftp, etc.
>
>ricardo
>ralvarado @
avantel .
com .
mx
>
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