Polyteknisk Boghandel

sendmail Milters teaches system administrators how to use a great tool to help eliminate spam!

Preface
xiii

Part I The Nefarious Spam Problem 1
Chapter 1 Gorilla Versus Guerrilla 3
1.
1 When a Gorilla Sneezes 4
1.
2 When a Guerrilla Masquerades as You 5
1.
3 The Major Proposals for Standards 6
1.
4 Email Fraud 7
1.
5 The Cost of Spam Suppression 9
1.
6 Vikings 10
Chapter 2 The Characteristics of Spam Email 11
2.
1 Connection Behavior 12
2.
2 Relaying through MX Servers 13
2.
3 Falsifying the Envelope Sender Address 15
2.
4 Disguising the Subject: Header 16
2.
5 Camouflaging the HTML Body 18
2.
6 Attempting to Fool Signature Detectors 23
2.
7 Unnecessary Encoding 24
2.
8 Grokking the Site 26
2.
9 Loose Ends 38
2.
10 Think Like a Spammer 38

Part II Creating a Test Environment 41
Chapter 3 Setting Up a Bait Machine 43
3.
1 Choose Your Platform 44
3.
2 Set Up DNS Records 47
3.
3 Configure sendmail 50
3.
4 Set Up Logging 54
3.
5 Excluding Non-email Ports 56
3.
6 Make Sure the Machine Reboots 58
Chapter 4 Baiting the Hook 61
4.
1 Create Fake Recipients 61
4.
2 Protect Good Email 64
4.
3 Run a Web Server 65
4.
4 Post to a Usenet Group 67
Chapter 5 Preventive Measures 75
5.
1 Tell Users about Plus Addressing 75
5.
2 Turn Off EXPN and VRFY 77
5.
3 Mask Web Addresses 78
5.
4 Watch Out for finger 81

Part III The Parts of a sendmail Milter 83
Chapter 6 The Roles and Flow of a Milter 85
6.
1 A Milter's Role in the Middle 85
6.
2 A Milter from the Point of View of sendmail 86
6.
3 The Milter Flow 87
Chapter 7 The Milter-Library 97
7.
1 Overview 97
7.
2 main() 99
7.
3 The smfi Data Access Routines 113
7.
4 The smfi Modifier Routines 127
Chapter 8 The xxfi Handler Milter Functions 151
8.
1 Overview 153
8.
2 The xxfi Orientations 154
8.
3 Abort Logic 155
8.
4 xxfi_connect() Reviews the Connection 156
8.
5 xxfi_helo() Reviews SMTP HELO/EHLO 161
8.
6 xxfi_envfrom() Reviews SMTP MAIL FROM 165
8.
7 xxfi_envrcpt() Reviews SMTP RCPT TO 171
8.
8 xxfi_header() Reviews Headers 176
8.
9 xxfi_eoh Reviews at End of Headers 182
8.
10 xxfi_body Reviews Each Body Chunk 186
8.
11 xxfi_eom Reviews at End of Envelope 190
8.
12 xxfi_abort Handles Envelope Abort 197
8.
13 xxfi_close Handles Connection Cleanup 200

Part IV Nuts and Bolts 205
Chapter 9 Milters and the Environment 207
9.
1 Where to Run Your Milter 208
9.
2 Your Milter's User ID 210
9.
3 How to Start and Stop Your Milter 213
9.
4 Put Your Milter into the Background 217
9.
5 Handle Signals 219
9.
6 Anticipate MX Servers 221
9.
7 Status and Logging 225
9.
8 Consider Portability Early 226
9.
9 Avoid Memory Leaks 227
9.
10 Final Words 229
Chapter 10 User and Temporal Feedback 231
10.
1 Consider Architecture 231
10.
2 Model the End User 233
10.
3 Maintain a History 234
10.
4 Possible Feedback Mechanisms 237
10.
5 Whitelisting 241
10.
6 Graylisting 242
10.
7 Archive, Reject, or Pass Through Spam 244
10.
8 Dynamic Configurations 246
10.
9 In Summary 253
Chapter 11 Handy Routines for the Message Body 255
11.
1 Parsing MIME-Encoded Boundaries 256
11.
2 Decoding Base64 Encoding 258
11.
3 Decoding Quoted-Printable Encoding 265
11.
4 Decoding Character-Entity Encoding 269
11.
5 Decoding URL-Encoding 277
11.
6 Stripping HTML Comments 279
11.
7 How to Use /etc/magic 284
11.
8 How to Use /usr/share/dict/words 288
11.
9 More 293
Appendix A Useful Source Code 295 Bibliography 297
Index 307