Fighting email spam and anti-UBE pointers

Archive-name: mail/anti-ube-pointer
Posting-Frequency: 2 times a month
Maintainer: Jari Aalto A T cante net

Announcement: "Bounces, Challenge-response systems, MTA, Bayesian tools (article pointer)"

Availability

FAQ archive is at http://www.faqs.org/faqs/

This message is an excerpt from bigger from Procmail Module
Library project's README.html document titled "Procmail
strategies against spam." available at
http://pm-lib.sourceforge.net/

The key points discussed in the document:

- Auto-replying or bouncing is considered a bad tactic
- MTA rejects can be abused and system administrators should
check their setup at least in regard to viruses.
- Challenge-Response system is based on false assumption that sender's
address can be used for authentication. It cannot and thus any C-R
system will contribute nothing else by amplifying the spam problem.

See picture http://pm-lib.sourceforge.net/pic/cr-system-joe-job.png

What should be done then?

- Bayesian tools are non-intrusive, harm no third parties
(in contrast to C-R), are easy to use and provide a good shelter.
- Battery of bayesian tools give even better shield due to
each program using a slightly different algorithm.

Many clarifying pictures are included:

- How address harvesting works
- How viruses should not be treated (at MTA level)
- Challenge-Response based authentication (overview)
- Challenge-Response system causing "Joe-Job"
- How MTA level UBE prevention works
- Procmail with battery of statistical tools

Table of contents:

1.0 Thoughts about increasing spam annoyance
1.1 Bouncing messages do no good
1.2 Rule based systems are not the solution
1.3 Challenge-Response systems make matters worse
1.3.1 Challenge-Response is not a doorbell but a
gun shooting decoys
1.3.2 Questioning Challenge-Response systems implementations
1.3.3 Summary - What are the effects of Challenge-Response
systems
1.4 Spam appearing in your yard - a story

2.0 A lightweight UBE block system with pure procmail
2.1 Suitable for accounts which ...
2.2 Where to put "pure procmail" UBE checks?
2.3 Using Procmail Module Library to fight spam

3.0 A heavyweight UBE blocking system
3.1 Advice for Debian Exim 4 mail system administrator
3.2 Advice for the normal account
3.3 Configuring Bayesian programs
3.4 A heavyweight spam catch setup using procmail

Some terminology

._UBE_ = Unsolicited Bulk Email
._UCE_ = (subset of UBE) Unsolicited Commercial Email

_Spam_ = Spam describes a particular kind of Usenet posting (and
canned spiced ham), but is now often used to describe many kinds of
inappropriate activities, including some email-related events. It
is technically incorrect to use "spam" to describe email abuse,
although attempting to correct the practice would amount to tilting
at windmills.

_Spam_ = definition by Erik Beckjord. "Some people decide that Spam
is anything you decide you want to ban if you can't handle the
intellectual load on a list." Remember, not to be confused with
real spam, which is unwanted bulk mail.

People are nowadays seeking a cure which will stop
or handle UBE. That can be easily done with procmail (under your
control) and with sendmail (by your sysadm). In order to select the
right strategy against UBE messages, you should read this section
and then decide how you will be using your procmail to deal with it.

Re: Fighting email spam and anti-UBE pointers

On 06 Mar 2005 05:29:50 GMT, (Jari
Aalto+mail.procmail) <> wrote:

> Archive-name: mail/anti-ube-pointer Posting-Frequency: 2 times
> a month Maintainer: Jari Aalto A T cante net
>
> Announcement: "Bounces, Challenge-response systems, MTA,
> Bayesian tools (article pointer)"
>
> Availability
>
> FAQ archive is at http://www.faqs.org/faqs/
>
> This message is an excerpt from bigger from Procmail
> Module Library project's README.html document titled
> "Procmail strategies against spam." available at
> http://pm-lib.sourceforge.net/
>
> The key points discussed in the document:
>
> - Auto-replying or bouncing is considered a bad tactic

That's absurd. Almost every corporation and organization in
the world does both.

You don't think that letting people know that their mail was
received (rather than being eaten by one of the dated spam
filters you recommend) or couldn't be delivered is a good idea?

> - Challenge-Response system is based on false assumption
> that sender's address can be used for authentication.

That's ridiculous. Challenge-Response systems are based upon the
assumption that spammers and trolls are using false return
addresses.

Which is true, 99.999% of the time.

Whoever produced this document is either extremely ignorant or
deliberately misleading the public.

Considering how many times they have been informed of its
erroneous content, the latter is the only reasonable conclusion.

Spammers and trolls HATE Challenge-Response systems, because theycannot beat them.

They can, however, beat the filters recommended in this post, and
do so all the time, because they are the world's foremost experts
in their use.

That's their _job/hobby_ They don't have anything else to do
with their time but figure out how to get their garbage in your
mailboxes.

And they can post whatever they want on the Usenet and the Web,
like anyone else.

Like this bi-weekly DISINFORMATIONAL article.

I wrote a simple Challenge-Response program that uses Procmail as
it's back end, and spam is no longer a part of my life. Period.

I don't even know when the spammers and trolls _try_ to get into
my mailboxes: Anonymous mail is rejected.

But no one I want to hear from has any problem reaching me.

Earthlink, as well as many other ISPs, offer Challenge-Response
systems as one of their basic spam-fighting tools.

Please Google the subject to get a real handle on it.




AC

alanconnor
AT
earthlink
DOT net

Re: Fighting email spam and anti-UBE pointers

Alan Connor writes:

| On 06 Mar 2005 05:29:50 GMT, (Jari
| Aalto+mail.procmail) <> wrote:
|
| > Archive-name: mail/anti-ube-pointer Posting-Frequency: 2 times
| > a month Maintainer: Jari Aalto A T cante net
| >
| > Announcement: "Bounces, Challenge-response systems, MTA,
| > Bayesian tools (article pointer)"
| >
| > Availability
| >
| > FAQ archive is at http://www.faqs.org/faqs/
| >
| > This message is an excerpt from bigger from Procmail
| > Module Library project's README.html document titled
| > "Procmail strategies against spam." available at
| > http://pm-lib.sourceforge.net/
| >
| > The key points discussed in the document:
| >
| > - Auto-replying or bouncing is considered a bad tactic
|
| That's absurd. Almost every corporation and organization in
| the world does both.

[Sender's Newsgroup mass-posting removed]

In today's world any vacation(1) like autoreply program is
potentionally creating an open spam relay.


| > - Challenge-Response system is based on false assumption
| > that sender's address can be used for authentication.
|
| That's ridiculous. Challenge-Response systems are based upon the
| assumption that spammers and trolls are using false return
| addresses.

To my knowledge, it is not possible to derive from SMTP MAIL FROM:
handshake that the offered address can be trusted as genuine. This is
the basis of C-R authentication. And the basis does not hold water.

| I wrote a simple Challenge-Response program that uses Procmail as
| it's back end, and spam is no longer a part of my life. Period.

When I have the time, I'll review of your procmail based solution;
with lot of pictures and arrows pointing out its supremacy - it may be
interesting to see if it will do what you claim it to do.

If anyone is interested in putting Alan'n "solution" for a review,
I've mirrored his code (in case it disappears from his site) at:

http://cante.net/mirror/users/connor-alan/

The original code was 2004-11-05 at

http://home.earthlink.net/~alanconnor/elrav1/

Jari