TweetFollow Us on Twitter

Review: SpamAssassin

Volume Number: 19 (2003)
Issue Number: 6
Column Tag: Reviews

Review: SpamAssassin

Regaining Control of your Inbox

by Vicki Brown

Ready, aim, fire!

Separating the Wheat from the Chaff

The popularity of the Internet, plus increases in connectivity (and email access), has given rise to a corresponding avalanche of spam. We all know what spam is - unsolicited junk email offering goods or services that we don't want, don't need, and often didn't want to know existed! We all agree that we would like less of it. Failing that, how can we wade through it, manage it, and delete it without losing our desirable mail (or our minds) in the process?

Many "solutions" have been proposed to deal with the spam problem. These range from anti-spam filters integrated inside email applications (e.g., the junk mail filters in Apple's Mail) to standalone products of various levels of complexity, ease of use, effectiveness, and cost.

My current solution of choice is SpamAssassin (http://www.spamassassin.org), in combination with procmail (http://www.procmail.org). I post-process the results through my desktop email client, (Eudora), for a very powerful and accurate spam-killing solution.

SpamAssassin provides many features, including:

  • user-configurable spam score threshold

  • ability to re-write Subject lines

  • user-configurable filters, using Perl regular expressions

  • modification of existing Spam scores

  • use of statistical, "Bayesian" analysis

  • "auto-learning"

  • optional use of DNS blacklists (e.g., Real-time Blackhole List)

  • optional use of Network Checksum Tests (services that compare message checksums to known spam)

  • "whitelists" (From addresses that are considered OK)

  • Accepted message languages

Note that SpamAssassin and procmail both run on the server side (where mail is originally delivered), not on the client side (i.e., usually not on the desktop) and neither has a GUI front end or a particularly "user-friendly" configuration mode. If you, or your users, are not technically inclined, I recommend that you choose a different path. However, if you enjoy tinkering, have some understanding of regular expressions (e.g., you've used Perl) and like to work with text-based configuration files, you will find the SpamAssassin/procmail combination to be powerful, flexible and, more important, accurate.

Configuration

SpamAssassin comes pre-configured with a large set of tests that it will perform on all incoming mail. In addition, you can add new tests, skip tests, raise or lower the "score" assigned by a given test or, using procmail, cause some mail to skip SpamAssassin altogether. Goto http://www.spamassassin.org/doc.html to see more detailed documentation. You'll even find a pointer, at that URL to a SpamAssassin configuration generator tool, designed to make it easier to customize an installation of SpamAssassin with some common options.

Much of the power of SpamAssassin comes from its configurability, its use of Perl regular expression pattern matching, and its interaction with procmail.

For example, many spammers have started adding ever-changing sets of numbers to the ends of subject lines, to fool the simpler junk mail filters. One GUI-based anti-spam application I tried had a set of filters designed to try to catch mail of this form. The filters looked like this:

   if Subject ends in 0
or if Subject ends in 1
or if Subject ends in 2
...
or if Subject ends in 9

This is rather cumbersome; worse, it doesn't handle the spammers who throw in a space at the very end. SpamAssassin's approach is both shorter and more flexible. This regular expression matches any digit, followed by 0 or more whitespace characters, at the end of the Subject line.

Subject =~ /\d\s*$/

SpamAssassin's interaction with procmail also allows me to specify whether mail is even sent through the SpamAssassin filters. For example, I can specify that mailing list messages should be delivered directly. This procmail recipe checks the message headers for one that matches the given Reply-to string, sending mail from the SpamAssassin-Talk list to my pre-defined default mailbox, without further processing.

:0 H
* ^Reply-to:.*spamassassin-talk
$DEFAULT

Results

SpamAssassin doesn't actually delete any spam. Instead, it tags each piece of mail it processes with a set of headers, e.g.,

X-Spam-Status: Yes, hits=6.2 required=2.5
tests=AWL,CLICK_BELOW,FREE_TRIAL,HTTP_WITH_EMAIL_IN_URL,
spam_PHRASE_05_08,VLB_spam_OFFER_4,VLB_TO_NOT_NAME,WEB_BUGS
version=2.43
X-Spam-Flag: YES
X-Spam-Level: ******
X-Spam-Checker-Version: SpamAssassin 2.43 (1.115.2.20-2002-10-15-exp)

X-Spam-Flag is a simple Boolean; if a message is considered potential spam, the flag is set (and the value is YES). X-Spam-Level provides more information; one "*" is given for each integer value of the spam score. X-Spam-Status provides full scoring information as well as which tests passed. Note that some tests raise the spam score while others are designed to lower it. After all tests have been run, the resulting score is compared to a (user configurable) threshold. If the score exceeds the threshold, the message is tagged as spam.

The user gets to decide how to handle the mail after it's been processed and tagged. One possibility is to continue processing with procmail. For example, the SpamAssassin docs assert that mail with a score of 15 or higher is almost certainly spam (with 0.05% false positives, according to SpamAssassin's rules/STATISTICS.txt file). After some use, I decided to lower this cutoff even more. I have configured procmail to delete any mail tagged with a Spam score of 10 or higher, using the following recipe:

:0:
    * ^X-Spam-Level: \*\*\*\*\*\*\*\*\*\*
    /dev/null

Other than that, all remaining mail is delivered. I have occasionally found false positives in mail with scores of less than 10; I want to check that mail by eye.

Here's where my third tool comes in. I use Eudora as my mail application and make extensive use of Eudora's filter mechanism to post-process my potential spam. I separate potential spam by mailboxes and labeling, based on certain criteria such as whether the message contains my full name (or only my email address), how high the spam score is, and any other interesting criteria. I scan the "Junk" mailboxes a few times a day, pull out false positives (setting new filters to catch those the next time!), and trash the real junk.


Installation

This is only a review, not a tutorial, so the installation section will hand wave a lot. You'll need a server machine running some variant of *nix (e.g., FreeBSD, Linux, or Mac OS X). If your server runs Mac OS X, you'll need to make sure it has been configured to deliver mail locally (e.g., using sendmail or qmail). How to set up a server is beyond the scope of this review.

You should also note that, although SpamAssassin can be run without procmail, its flexibility (and power) increases when it is used in conjunction with procmail. SpamAssassin does not include code to handle local mail delivery; it relies on procmail (or something else) for delivery. Unless you know that a reliable "something else" is available, use procmail.

Procmail may already be on your server; it is pre-installed on most *nix systems these days (use whereis procmail or locate procmail to check, then read the documentation to determine how to configure procmail for your server situation). If it's not pre-installed, download and build procmail from the procmail.org web site.

SpamAssassin is probably not pre-installed on your system; however, installation is simple. In fact, you'll probably be able to install it without first downloading the archive. SpamAssassin is written as a Perl module; the easiest way to install it is by using Perl's CPAN shell (from the command line, as root):

perl -MCPAN -e shell 
o conf prerequisites_policy ask
install Mail::SpamAssassin
quit

Alternatively, you can always download the latest archive from spamassassin.org, then build and install SpamAssassin according to the documentation. If you have any problems, be sure to read the Installation notes on the SpamAssassin site. Check the documentation for more information on configuration, as well as useful options.

Summary

If you're looking for a powerful, flexible, and accurate solution to the spam problem, I recommend that you consider the team of SpamAssassin and procmail. Both programs are free and come with example recipes and suggestions for how to use them to your best advantage. Each has a support community that you can draw upon for assistance and ideas, as well as mailing lists to keep you informed. If you have a server on which to install it (note that SpamAssassin can be installed server-wide or on a per-user basis) and know (or are willing to learn about), regular expressions, SpamAssassin may be the spam-killing tool you've been looking for. Give it a try.

References


Vicki Brown

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Google Earth 7.1.7.2602 - View and contr...
Google Earth gives you a wealth of imagery and geographic information. Explore destinations like Maui and Paris, or browse content from Wikipedia, National Geographic, and more. Google Earth combines... Read more
ClamXav 2.10 - Virus checker based on Cl...
ClamXav is a popular virus checker for OS X. I have been working on ClamXav for more than 10 years now, and over those years, I have invested a huge amount of my own time and energy into bringing... Read more
Tweetbot 2.4.4 - Popular Twitter client.
Tweetbot is a full-featured OS X Twitter client with a lot of personality. Whether it's the meticulously-crafted interface, sounds and animation, or features like multiple timelines and column views... Read more
Sierra Cache Cleaner 11.0.1 - Clear cach...
Sierra Cache Cleaner is an award-winning general purpose tool for macOS X. SCC makes system maintenance simple with an easy point-and-click interface to many macOS X functions. Novice and expert... Read more
Things 2.8.8 - Elegant personal task man...
Things is a task management solution that helps to organize your tasks in an elegant and intuitive way. Things combines powerful features with simplicity through the use of tags and its intelligent... Read more
Remotix 4.1 - Access all your computers...
Remotix is a fast and powerful application to easily access multiple Macs (and PCs) from your own Mac. Features Complete Apple Screen Sharing support - including Mac OS X login, clipboard... Read more
Airfoil 5.1.2 - Send audio from any app...
Airfoil allows you to send any audio to AirPort Express units, Apple TVs, and even other Macs and PCs, all in sync! It's your audio - everywhere. With Airfoil you can take audio from any... Read more
Firefox 49.0.1 - Fast, safe Web browser.
Firefox offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals and casual... Read more
Default Folder X 5.0.7 - Enhances Open a...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click on... Read more
Safari Technology Preview 10.1 - The new...
Safari Technology Preview contains the most recent additions and improvements to WebKit and the latest advances in Safari web technologies. And once installed, you will receive notifications of... Read more

4 games like Burly Men at Sea to inspire...
Burly Men at Sea is out today and it looks a treat. It tells the tale of three Scandinavian fishermen who leave the humdrum of their daily lives to go exploring. It’s a beautiful folksy story that unfurls as you interact with the environment... | Read more »
3 reasons you need to play Kingdom: New...
Developed by a tag team of indie developers - Thomas "Noio" van den Berg and Marco "Licorice" Bancale - Kingdom is a vibrant medieval fantasy adventure that casts players as a king or queen who must expand their empire by exploring the vasts lands... | Read more »
JoyCity have launched a brand new King o...
Great news for all of you Game of Dice fans out there - JoyCity have just released a brand new limited edition pack with a really cool twist. The premise of Game of Dice is fairly straightforward, asking you to roll dice to navigate your way around... | Read more »
Burly Men at Sea (Games)
Burly Men at Sea 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Burly Men at Sea is a folktale about a trio of large, bearded fishermen who step away from the ordinary to seek adventure. | Read more »
3 tips for catching the gnarliest waves...
Like a wave breaking on the shore, Tidal Rider swept its way onto the App Store charts this week settling firmly in the top 10. It’s a one-touch high score-chaser in which you pull surfing stunts while dodging seagulls and collecting coins. The... | Read more »
The beginner's guide to destroying...
Age of Heroes: Conquest is 5th Planet Games’ all new turn-based multiplayer RPG, full of fantasy exploration, guild building, and treasure hunting. It’s pretty user-friendly as far as these games go, but when you really get down to it, you’ll find... | Read more »
Infinite Tanks (Games)
Infinite Tanks 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: | Read more »
Agatha Christie - The ABC Murders (FULL)...
Agatha Christie - The ABC Murders (FULL) 1.0 Device: iOS Universal Category: Games Price: $6.99, Version: 1.0 (iTunes) Description: Agatha Christie: The ABC Murders Your weapon is your knowledge. Your wits will be put to the ultimate... | Read more »
HeadlessD (Games)
HeadlessD 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: HeadlessD is hand-painted dungeon crawler with intuitive touch controls and NO in-app purchases. | Read more »
Leaf for Twitter (Social Networking)
Leaf for Twitter 1.0.1 Device: iOS iPhone Category: Social Networking Price: $4.99, Version: 1.0.1 (iTunes) Description: | Read more »

Price Scanner via MacPrices.net

Apple refurbished 2015 13-inch MacBook Airs a...
Apple has Certified Refurbished 2015 13″ MacBook Airs available starting at $759. An Apple one-year warranty is included with each MacBook, and shipping is free: - 2015 13″ 1.6GHz/4GB/128GB MacBook... Read more
MacBook Airs on sale for up to $100 off MSRP
B&H Photo has 13″ and 11″ MacBook Airs on sale for up to $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 11″ 1.6GHz/128GB MacBook Air: $799 $100 MSRP - 11″ 1.6GHz/256GB... Read more
Apple refurbished 12-inch 128GB iPad Pros ava...
Apple has Certified Refurbished 12″ Apple iPad Pros available for up to $160 off the cost of new iPads. An Apple one-year warranty is included with each model, and shipping is free: - 32GB 12″ iPad... Read more
Phone2Action Unveils New Voter Turnout Techno...
Phone2Action, a leading digital advocacy platform, today launched its Tech to Vote Civic Action Center digital advocacy and communications platform on National Voter Registration Day September 27.... Read more
Apple & Deloitte Team Up to Help Business...
Apple and international professional services firm Deloitte have announced a partnership to help companies quickly and easily transform their workflow dynamics by maximizing the power, ease-of-use,... Read more
Chop Commute – See Traffic and Drive Times on...
Shrewsbury, Massachusetts based Indie developer, InchWest has released Chop Commute 1.61, a Mac app that takes the guesswork out of daily commute by showing real-time traffic and drive times right on... Read more
12-inch 32GB WiFi iPad Pros on sale for $50 o...
B&H Photo has 12″ 32GB WiFi Apple iPad Pros on sale for $50 off MSRP, each including free shipping. B&H charges sales tax in NY only: - 12″ Space Gray 32GB WiFi iPad Pro: $749 $50 off MSRP -... Read more
Recent price drops on refurbished iPad minis...
Apple recently dropped prices on several Certified Refurbished iPad mini 4s and 2s as well as iPad Air 2s. An Apple one-year warranty is included with each model, and shipping is free: - 16GB iPad... Read more
Apple refurbished Mac minis available startin...
Apple has Certified Refurbished Mac minis available starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: - 1.4GHz Mac mini: $419 $80 off MSRP - 2.6GHz Mac... Read more
13-inch 2.5GHz MacBook Pro available for $928...
Overstock has the 13″ 2.5GHz MacBook Pro available for $927.99 including free shipping. Their price is $171 off MSRP. Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Restaurant Manager (Neighborhood Captain) - A...
…in every aspect of daily operation. WHY YOU'LL LIKE IT: You'll be the Big Apple . You'll solve problems. You'll get to show your ability to handle the stress and Read more
*Apple* Wireless Lead - T-ROC - The Retail O...
…wealth of knowledge in wireless sales and activations to the Beautiful and NEW APPLE Experience store within MACYS.. THIS role, APPLE Wireless Lead, isbrandnewas Read more
Lead *Apple* Advocate - T-ROC - The Retail...
…Company, is proud of its unprecedented relationship with our partner and client, APPLE ,in bringing amazing" APPLE ADVOCATES"to "non" Apple store locations. Read more
*Apple* Advocate - T-ROC - The Retail Outsou...
…Company, is proud of its unprecedented relationship with our partner and client, APPLE ,in bringing amazing" APPLE ADVOCATES"to "non" Apple store locations. Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.