Re: blocking dialups

[torben fjerdingstad <]

On Tue, Oct 13, 1998 at 09:44:42AM +0100, Clive D.W. Feather wrote:
> torben fjerdingstad said:
> > First, I think the ISP's should filter their dialups so they have
> > to relay through the local mail relay.
> 
> Not this old chestnut again ?

Oh - old topic. I did not know that.

> If you bring this up on SPAMTOOLS-L, you will discover that there is a very
> diverse range of opinion on the topic. There are *lots* of legitimate uses
> for direct unrelayed mail.

Can you mention just one reason for not relay through the ISP's
mail server (except for sending spam)?

> > Until then, I would like to block all dialup/ppp ip's.
> > They are easy to find.
> 
> Oh yes ?

Just look at the messages from mailer-daemon to find some dialup
spammers and do reverse lookups for the classe C network they
came from. I found a nice program for that at www.rootshell.com.
Sample output:
195.66.232.18 => guest1.linx.org
195.66.232.19 => guest2.linx.org
195.66.232.20 => guest3.linx.org

The hostnames usually clearly indicate if they are dialups.
Try to ping a few of them for verification. Or telnet
to the smtp port if really in doubt.

In your case I am in doubt because there are so few of them,
and I have not received any spam from them.

My problem remains to find out when a net used for dialups
is transferred to some other purpose.

-- 
Med venlig hilsen / Regards 
Netdriftgruppen / Network Management Group
UNI-C          

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