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Comment by apo | Hacker News Reader

Spam countermeasures have led to some fascinating new technologies. In addition to the one cited in the article was Hashcash, which was developed a few years earlier:

http://www.hashcash.org/papers/hashcash.pdf

Hashcash requires the sender to expend a small quantity of computational work, and attach a proof of this to the email before a recipient even opens it. The underlying assumption is that the burden would be insignificant for a real email sender, but onerous for a spammer.

The approach inspired the powerful anti-spam system at the center of Bitcoin.

It might be interesting to catalog all of the most innovative early approaches to combating spam, and the unrelated technologies that later arose from them.

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I recently came across this idea to prevent friend request spam on social media, using the Lightning network. The idea is that the person sending you the friend request must attach a small amount of money (in the form of a special lightning payment). If the friend request is legitimate, you can accept it (and not claim the money). But if it's spam you reject the friend request but take the money instead. This is different than Hashcash in that it incurs real monetary costs to the attacker. Instead of using compute resources (for the mining algorithm), the money would actually end up in your pocket.

A much older example is the high cost of sending text messages basically eliminates text message spam.

Except the cost of phone calls, text messages and even postal mail is sufficiently low to result in spam across all three mediums in ever larger quantities than before

As he said, it is a much older version. As with everything the cost decreases over time to the point that it no longer outweighs benefit.

Put another way, this is the unfortunate flip side of free unlimited talk and text.

I don't think this would work in real life. When Bill Gates was proposing something similar, one of the engineers on the anti-spam team built an FPGA that would allow a spammer to solve such puzzles quickly enough to prevent spamming. His observation to me was that even though such a technique would work, botnets had eliminated the need for specialized hardware.

Not to mention that spam is frequently sent by pwnd boxen or botnets. Why would the attacker care that it racks up someone else's electricity bill?

How does that work for free email newsletters? They're typically already paying an email service provider. Having to pay even more could be onerous for large, double opt-in lists, even though they're not spamming.

I'm guessing that 99% of newsletters are sending vastly fewer messages than the people who send me half a dozen "Welcome to Adulte Sex " messages a day.

Maybe, but spammers are also more likely to be sending from rented botnets that can handle the increase in CPU usage spread over a large number of other people's computers.

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