ZyXEL ZyWALL 5 User Guide - Page 325

Chapter 16 Anti-Spam Screens SpamContent Engine The SpamContent engine examines the e-mail's content to decide if it would generally be considered offensive. The vocabulary design, format and layout are considered as part of thousands of checks on message attributes that include the following. • To Field • Subject Field • Header Fields • Email Format, Design, and Layout • Vocabulary, Word Formatting and Word Patterns • Foreign Language Detection • SMTP Envelope Content and Analysis • Country Trace • Image Layout Classification • Hyperlink Analysis and Comparison • Contact Verification The SpamContent engine parses words into pieces to detect similar vocabulary even if the words do not match exactly. The anti-spam external database also performs Bayesian statistical analysis on the e-mail's content. The engine uses artificial intelligence technology to 'learn' over time, as spam changes. SpamTricks Engine The SpamTricks engine checks for the tactics that spammers use to minimize the expense of sending lots of e-mail and tactics that they use to bypass spam filters. Use of relays, image-only e-mails, manipulation of mail formats and HTML obfuscation are common tricks for which the SpamTricks engine checks. The SpamTricks engine also checks for "phishing" (see Section 16.2 on page 315 for more on phishing). ZyWALL 5/35/70 Series User's Guide 325