Commentary — Opposite to what Randall Stross suggests is his New York Times column, computational puzzles are not a relevant solution to stop spam.
What we need, in other words, is (…) a way to force a sender to pay every time a message was sent
– payment not in money, but in time, by applying the computer’s resources to a computational puzzle, devised on the fly for that particular message.
Hijacking an end-user’s machine to have it digitally stamp messages will let spammers bypass this stamp rule. In the end, ideas such as this will only cripple end-users even more. And this should have been obvious to the author given the considerable amount of coverage Spamhaus got for its warning on the threat from proxy hijackers.