Re: Hardening lists against spam attacks

["Frank O'Dwyer" <fod@brd.ie>]

> > It would be nice if each user could install filters on Majordomo itself.
> > Not only would we not need to buy Eudora Pro, but we wouldn't have to
> > pay to download messages we didn't want to read, and without having
> > to employ a moderator (censor).
>  
> Bad idea.  It's tough enough on the host running a list with 1500 or
> 2000 people on it.  Adding outbound filtering for each user would
> be a real burden on the list host.  It's better to distribute the
> processing by making the user agent (or mail transport that's delivering
> to the user) do the filtering.

I guess you're not paying for your mail then :-)  Just stand back from
this for a moment -  doesn't it seem just nonsensical to have a robot 
(majordomo) cranking out 10s of messages to 1000s of users, day in day 
out, just for other robots (filters) to delete them?  And to pay for 
the privilege?

I mean, is it really better to consume the cycles on _everybody's_ 
machine, _plus_ use all that bandwidth? I'd say that's not obvious.  
Granted, it takes my creaking old 486 about 10 minutes for exmh to do 
a filtered 'inc' on the new mail. However I have to pay the phone bills 
to download all the cruft in the first place, just in order to get the 
rare nugget. And I can't use my mailer while the 'inc' is running. And if 
everyone else is paying and and waiting too, then maybe it turns out to 
be better for the messages to be filtered centrally, so we all waste less 
time and money, even if the server does heat up a little. (Hell, I might 
even chip in to upgrade the list server if that's what it took, and still 
save money.)

Besides, it's not necessarily true that filtering would make the server load
significantly worse (certainly not if PGP is the other option), or even 
that it makes it worse at all. For example, the overhead on doing a lookup 
on a short list of filtered users might well be more than offset by not 
having to send the message. (Having once seen a DEC alpha brought to its 
knees by 'sendmail', I can believe that...).  If processing turned
out to be a genuine problem then maybe the list could be split over 
several servers. (In an ideal world, of course, the filtering agents 
would be mobile, and would learn to back all the way up the pipe and 
would eventually run on the spammer's machines :-)

> In addition, a filtering majordomo will only 'protect' the lists that it
> serves.  I don't know about you but I get a lot of spam from all sorts
> of different sources.  I need to have a filter anyhow.  It's not hard to
> add some more rules to filter out each lists's bozos.  It's a lot
> simpler to do that than it would be to upload filter rules to each
> of the 10 or 12 listservers I get mail from.

True, but I'd sure love not to have to download some of the cruft down 
the old 28.8 line in the first place...I suppose IMAP would have the same
thing going for it but it's not here yet (plus you still have all that
list cruft that 99% of people filter or delete going up and down the 
internet).  

[ deletia ... The security issues you mention are real, but so are 
the solutions you mention :-) ]

Cheers,
Frank O'Dwyer.