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Re: DSL router and security

On Thu, Feb 10, 2000 at 01:22:19PM +0000, Howard Mann wrote:
> Hi,
> I use DSL with Slink. I previously had a static IP address. I used an IP Chains ruleset as one security level. All was well.
> My ISP recently mandated a configuration change for the Cisco DSL router from " bridging" to "ppp" mode, including NAT at the router level.
> The router now changes my assigned IP address to a private Class A address ( ). I changed my networking ( eth0) settings to reflect this.
> I guess I no longer need the IP Chains firewall. Is this correct ?

 You never need security.  It's nice to have, though!!! :)  You should leave
your firewall configured if it is possible for other people using the same
ISP to send you stuff that hasn't been filtered through your ISP's firewall,
or you don't trust everyone at the ISP with access to the network.

If other people can connect to an IP address which get's forwarded to yours
internally, then you should definitely leave your firewall up.  (MTT's
mpoweredpc ADSL service in Halifax is like this.  I have a cable modem
(Halifax has 2 high speed providers :), but people with ADSL tell me that
they have an internal IP and an external IP.  The internal is fixed, but the
external one changes all the time.  Presumably, though, if you know the
external IP, then you could connect to ports on the ADSL computer, rather
than just waiting for it to contact you.  This means it is succeptible to

> What security considerations/measures should I now adopt with respect to my new setup ?

 Don't trust anybody you don't know personnally.  Don't allow any access to
anyone who doesn't need it.  :)

> My knowledge of the function of this router is rudimentary.

 Better leave the firewall up, then.

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