David A. Wheeler's Blog

Tue, 16 Nov 2004

New Edition: Countering Spam by Using Ham Passwords (Email Passwords)

I’ve released a new version of my article, Countering Spam by Using Ham Passwords (Email Passwords). In particular, I’ve christened the approach with a new name: “ham passwords”. I’ve found that ham passwords are a simple and effective technique for countering spam; I use it myself. A ham password is a special password you ask strangers, or senders in general, to include in email they send to you, typically in the subject line. If the sender wants the receiver to receive an email, then the sender should send the ham password to prove that they are authorized to send the email. This technique is excellent in countering the major weakness of spam filters: incorrectly labelling ham as spam. This approach is inexpensive, requires no changes to any software code, and is simple to understand. It especially works well when combined with other techniques that handle non-strangers.

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