[Air-l] screening out spam

Tom Diffenbach diffenbach at comcast.net
Tue Aug 17 05:24:37 PDT 2004

There's another side effect to a strict set of filtering rules: you might
make it too hard for email that you'd like to get thru.   From the outside
world, I deal with academic email addresses where incoming email is
"scored".  If I want to be sure an email gets thru, I have to repeatedly use
words like "Professor" or the name of the school to raise my mail's score in
case a pic or some content might have somehow lowered its score.  I make the
effort; I wonder how many others quit trying to communicate with
academicians inside these walls.  I have found in non-email contacts that
some professors are not aware of the details of their school filters.

----- Original Message ----- 
From: "Frank Schaap" <architext at fragment.nl>
To: <air-l at listserv.aoir.org>
Sent: Tuesday, August 17, 2004 8:03 AM
Subject: Re: [Air-l] screening out spam

Gary Thompson wrote:
> The recent spate of messages from those trying to unsubscribe reminds me
> that about 2/3 of everything I get via e-mail—even with an academic
> address—is spam. I’ve got my “rules” set up so as to try to catch some
> of this:

Since you talk about "rules" I suppose you're using Microsoft Outlook

> --if the subject line contains certain keywords, e.g., “market,”
> “drugs,” “investment,” “penis,” “casino,” then it goes into my trash box.
> --if the from line contains “admin,” then it goes in the trash box
> --if the “to” says “undisclosed recipients,” etc.
> I’m wondering whether others have had success with similar rules, as
> opposed to installing spam-killing software (and as for that, how well
> does it work, when spammers garble key words so as to avoid screening,
> e.g., Vi*ag*kra or other combinations).

It helps a little... but unless your e-mail client lets you write
sophisticated regular expressions into the rules (which Outlook doesn't
afaik), you quickly end up with countless not terribly effective rules. I
tried this too before our department admins installed server side spam
filtering on the Exchange server.

One of the reasons that 'professional' spam fighters have moved beyond
'mere' rule based filtering is that because spamfilters have to be made
available to the public, dedicated spammers will quickly find ways around
static rules for filtering spam.

A Bayesian spamfilter is a more dynamic type of filter that goes through a
learning period in which you tell it which messages are spam and which
messages are ham. It classifies a number of characteristics of these
messages and depending on their statistical occurrence in either category
incoming messages are sorted into either the spam or the ham category.

Mozilla based e-mail clients such as the Mozilla Suite and Thunderbird
<http://mozilla.org> contain bayesian filters. Personally I'm very pleased
with the end result. I haven't seen a spam message up close for a long while
and I haven't had any false positives after a rather short training period.
The Mozilla based clients support both POP and IMAP.

But, if you just have to use Outlook to access your department's Exchange
server and your department admins refuse to install spamfiltering on the
server, you can run a bayesian filter in your own Outlook install (if
they've given you enough permissions to install it). Have a look at
Spambayes <http://spambayes.sourceforge.net/>

Eventually I guess we'll see some sort of authentication system that makes
e-mail traceable. For the moment I just try to keep my personal, non-list
related e-mail addresses off the web and out of newsgroups. For that kind of
use I set up free throw-away accounts that I use for a couple of months
untill they become useless.



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