The Canter & Siegel Usenet Spam

On April 12, 1994, husband-and-wife lawyers Laurence Canter and Martha Siegel executed the first massive commercial spam campaign in internet history. They used a Perl script to post an advertisement for their "Green Card Lottery" legal services to over 6,000 distinct Usenet newsgroups. Usenet was the decentralized discussion network of the early internet, governed by community norms rather than central moderators. This event, known as the "Green Card Spam," violated those norms so egregiously that it crashed multiple servers and enraged the global user base.

While typically viewed as internet trivia, this event is a critical milestone in the history of Bitcoin because it highlighted the economic vulnerability of open, decentralized networks. In a permissionless system like Usenet (or email), it costs almost nothing to send a message, but it costs resources (bandwidth, storage) to receive it. This asymmetry—cheap to attack, expensive to defend—is the fundamental problem of Sybil attacks and spam.

This incident directly motivated researchers to find ways to impose a cost on senders. Three years later, this line of thinking led Adam Back to propose Hashcash, a system that required email senders to compute a "Proof-of-Work" to prove they weren't spammers. The Green Card Spam incident demonstrated the 'tragedy of the commons' in free decentralized networks, motivating the invention of 'unforgeable costliness' (Proof-of-Work) mechanisms that Satoshi Nakamoto would later adapt to secure the Bitcoin network against similar abuse.

Key Sources:
• Wired: The Spam That Started It All
• Wikipedia: Canter & Siegel Incident
• Hashcash.org (Context on Spam prevention)