Spam-Fighting Terminology

A list of terms you should know.

Like any other specialized field, spam-fighting has developed its own terminology. Here’s a quick guide to some of the terms you may encounter when researching anti-spam products.

Bayesian. Bayesian analysis looks at relative word frequencies between good and bad e-mail to determine whether a particular e-mail is most likely spam or not. See the sidebar, “Understanding Bayesian Analysis.”

Blacklist. A list of addresses from which e-mail should never be accepted.

DNSBL. DNS Black List. An automated service that returns a code specifying whether it thinks a particular IP address belongs to a spammer. See the sidebar, “Using DNSBLs.”

False negative. Mail that should have been recognized as spam, but which was delivered as regular e-mail instead.

False positive. Mail that should have been delivered, but which was erroneously recognized as spam. Most users find false positives to be far worse than false negatives.

Ham. E-mail that the user wants to receive (the opposite of spam).

Quarantine. A holding pen for messages, from which they can be deleted or approved for delivery, either by the systems administrator or by an individual user.

Spam. Undesired e-mail of any sort. Sometimes called UCE or Unsolicited Commercial E-mail.

Web beacon. A single pixel linked image in an HTML e-mail. This is invisible to the user, but serves to tell the sender when a piece of mail has been opened.

Whitelist. A list of addresses from which e-mail should always be accepted.

Additional Information on Spam

Outrun the Avalanche

What's New in Exchange 2003

Understanding Bayesian Analysis

Two Services for the Enterprise

Using DNSBLs

A Thanks to Hormel

For more terminology and a catalog of spammers’ tricks for disguising their e-mails, see ActiveState’s “Field Guide to Spam” at

About the Author

Mike Gunderloy, MCSE, MCSD, MCDBA, is a former MCP columnist and the author of numerous development books.

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