Re: Administrative Overheads Arising from UCE

[Paul Mansfield <]

On Wed, 17 Feb 1999 cor@localhost wrote:
> > Why don't you just disable incoming connections to the port 25 for your dialup
> > users? You'd get much less hassle.
> 
> Unfortunately, in the real world, this isnt an option. End users in Holland
> are very aware of any kind of filtering, and start shouting censorship
> when you filter UDP port 31337, let alone port 25. It would indeed solve
> a lot of problems, but I doubt many dialup ISPs filter this port. If any
> do, please say so, and share your experiences. 

I believe that Freeserve (www.freeserve.net), a no-subscription ISP, use
redirection on dialups so that when you try and connect to a mail system it
ALWAYS goes to their own mail relays. Kind of like the way transparent WWW
caches work.

i.e. dialup into freeserve and then try telnet to relay1.mail.uk.psi.net and
you'll see the Freeserve mail system.

This means that smart hosts think they're connecting to the target specified by
the MX records, and dumb hosts just connect to their mail relays anyway, thus
avoiding complaints about filtering!

Thus freeserve can then ensure proper logging takes place, can rate-control
connections, apply automated spam filtering/blocking, add headers etc.

I've tried to spot a flaw in this system, but as long as you make sure you load
balance your mail relays with some sort of resilient system, I can't think of
one.


Paul
----
P Mansfield, Senior SysAdmin PSINet UK Ltd, +44-1223-577611 fax:~577600 
# You can wait for a bus-error all day and then three come along all at once #