Book Image

SpamAssassin: A practical guide to integration and configuration

Book Image

SpamAssassin: A practical guide to integration and configuration

Overview of this book

As a busy administrator, you know Spam is a major distraction in todays network. The effects range from inappropriate content arriving in the mailboxes up to contact email addresses placed on a website being deluged with unsolicited mail, causing valid enquiries and sales leads to be lost and wasting employee time. The perception of the problem of spam is as big as the reality. In response to the growing problem of spam, a number of free and commercial applications and services have been developed to help network administrators and email users combat spam. Its up to you to choose and then get the most out of an antispam solution. Free to use, flexible, and effective, SpamAssassin has become the most popular open source antispam application. Its unique combination of power and flexibility make it the right choice. This book will now help you set up and optimize SpamAssassin for your network.

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SpamAssassin: A practical guide to integration and configuration
Sep, 2004 | 240 pages
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Table of Contents (24 chapters)
SpamAssassin
SpamAssassin
Credits
Credits
About the Author
About the Author
About the Reviewers
About the Reviewers
Introduction
Introduction
Free Chapter
1
Introducing Spam
Introducing Spam
Defining Spam
The Costs of Spam
Spam and the Law
Summary
2
Spam and Anti-Spam Techniques
Spam and Anti-Spam Techniques
Spamming Techniques
Anti-Spam Techniques
Spam Filtering Services
Anti-Spam Tools
Summary
3
Open Relays
Open Relays
Email Delivery
Open Relay Tests
MTA Configuration
Summary
4
Protecting Email Addresses
Protecting Email Addresses
Websites
Usenet
Trojan Software
Mailing Lists and Archives
Registration for Websites
Employees
Business Cards and Promotional Material
How Spammers Verify Email Addresses
Summary
5
Detecting Spam
Detecting Spam
Content Tests
Header Tests
DNS-Based Blacklists
Statistical Tests
Message Recognition
URL Recognition
Examining Headers
Reporting Spammers
Valid Bulk Email Delivery
Summary
6
Installing SpamAssassin
Installing SpamAssassin
Building from Source
Using CPAN
Installing by Hand
Resolving Build Failures
Packaged Distributions
Verifying the Installation
Upgrading
Uninstalling
SpamAssassin Components
Summary
7
Configuration Files
Configuration Files
Configuration Files
Rule Files
Summary
8
Using SpamAssassin
Using SpamAssassin
SpamAssassin as a Daemon
SpamAssassin and Procmail
Integrating SpamAssassin into the MTA
Testing and Troubleshooting
Rejecting Spam
Summary
9
Bayesian Filtering
Bayesian Filtering
Scoring
Training
Confirming Operation
Filter Training
Disabling Bayesian Filtering
Summary
10
Look and Feel
Look and Feel
Headers
Reports
Subject Rewriting
Summary
11
Network Tests
Network Tests
RBLs
SURBLs
Vipul's Razor
Pyzor
DCC
Spamtraps
Summary
12
Rules
Rules
Writing Rules
Using Other Rulesets
Summary
13
Improving Filtering
Improving Filtering
Whitelists and Blacklists
The Auto-Whitelist
Resolving Incorrect Classifications
Character Sets and Languages
Summary
14
Performance
Performance
Bottlenecks
Performance Improvement Methodology
Using SQL
Summary
15
Housekeeping and Reporting
Housekeeping and Reporting
Separating Levels of Spam
Detecting When SpamAssassin Fails
Spam and Ham Reports
Summary
16
Building an Anti-Spam Gateway
Building an Anti-Spam Gateway
Choosing a PC Platform
Choosing a Linux Distribution
Configuring Postfix
Installing Amavisd-new
Configuring Amavisd-new
Configuring Postfix to Run Amavisd-new
Configuring External Services
Firewall Configuration
Backups
Testing
Going Live
Summary
17
Email Clients
Email Clients
General Configuration Rules
Microsoft Outlook
Microsoft Outlook Express
Mozilla Thunderbird
Qualcomm Eudora
Summary
18
Choosing Other Spam Tools
Choosing Other Spam Tools
Spam Policies
Evaluating Spam Filters
Configuring the Second Filter
Other Techniques
Summary
Glossary
Glossary

Chapter 11. Network Tests

SpamAssassin on its own can detect a high proportion of spam. By using network tests, spam detection can be further improved. SpamAssassin includes support for Realtime BlockLists (RBLs) and Spam URI Realtime BlockLists (SURBLs). All these external services are easy to integrate into SpamAssassin.

The effectiveness of network tests varies from a 60% detection rate upwards. By using them in conjunction with SpamAssassin, spam detection rates are much higher, typically over 95%! However, network tests slow down spam detection. This means that the SpamAssassin processes will take longer to complete and will increase the memory usage of the email server.

This chapter describes the support SpamAssassin has for RBLs and SURBLs, and focuses on three external services:

  • Vipul's Razor

  • Pyzor

  • The Distributed Checksum Clearinghouse (DCC)

RBLs are blocklists of known sources of spam. By default, SpamAssassin uses a number of RBLs to check the source of the email.

A SURBL is a blocklist...

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