Beat Spam Using Hashcash

Shell writes "If they want to send spam, make them pay a price. Built on the widely available SHA-1 algorithm, hashcash is a clever system that requires a parameterizable amount of work on the part of a requester while staying "cheap" for an evaluator to check. In other words, the sender has to do real work to put something into your inbox. You can certainly use hashcash in preventing spam, but it has other applications as well, including keeping spam off of Wikis and speeding the work of distributed parallel applications." If you're specifically interested in hashcash for your mail server, Camram has some interesting ideas -- their Frequently Raised Objections page may be illuminating.

Comments

Re:Greylisting worked for my company

[Haegar]

Tried it at work - stopped loads of spam, but had to disable it because out there are too many broken smtp servers (on short inspection mostly lotus notes) that think an return code of 4xx is a permanent error and bounce the mail.

And my boss is not happy when even ONE important mail from a client is not reaching him.