Tavis Ormandy called this, about Anubis, almost exactly a year ago:

https://news.ycombinator.com/item?id=44962529

It never really cohered as a solution. High-powered scrapers are better equipped to handle proof-of-work challenges than end users. Proof of work makes sense for a password hash, where any one guess at a password provides zero marginal utility. But every request from a scraper is productive to the scraper.

▲ harshreality 5 hours ago | parent | next [-]

If you want to argue that there's excessive enthusiasm about anubis, which is neither a permanent solution nor a solution against all bots run for all purposes (some bot authors are cleverer than others, and you don't have to block everything, just enough to reduce resource use to tolerable levels)... fine.

However, the refrain from naysayers isn't that there's too much enthusiasm. It's that anubis doesn't make sense as a theoretical barrier against bots. Who cares as long as it works empirically, even briefly? Are you suggesting people let their sites continue to be degraded or unusable until they find a better solution, even though PoW challenges can improve the situation today?

Not everyone has the luxury of writing their own web app designed to handle massive bot traffic at minimal cost, gutting functionality to meet that requirement if necessary.

I noticed a couple of weeks ago that 1-2 orders of magnitude more bots were getting past anubis challenges. However, it would be incorrect to conclude that it's doing nothing and now worthless aside from heating up visitors' cpus. If I turn it off, I see >2x bots.

The next salvo in the war of attrition will probably be when anubis switches to wasm hashx, which the author suggested, in previous HN threads, is on the roadmap.

If bots quickly adapt (Claude vibe-coded JIT wasm-to-native-transpiler for hashx challenge algorithms?), that may be the end of anubis and efforts like it. If they don't, I expect more HN threads with people complaining that such compiler efforts are possible and therefore PoW-gated sites are doing it wrong... even if those sites stay usable.

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tptacek 5 hours ago | parent [-]

I'm not moralizing. The sites running Anubis are owned by people who like Anubis and are fully within their rights to run Anubis. I don't care how enthusiastic they are about it. It's their call.

I'm just saying, it's bad computer science.

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harshreality 4 hours ago | parent | next [-]

You're arguing worst-case, and people running anubis are saying it dramatically helps in their experience, because they're not getting too many of the sorts of bots that people like you and Tavis (correctly) argue are theoretically possible. So the argument that it's "bad CS" falls flat.

A better, perhaps the best, argument is that a worse bot mix might appear tomorrow, so anubis should be used as a runway for a better solution, and not as a solution in itself. If only everyone with a website had the desire (or AI tokens) to implement their own better solution. In some cases even desire or a lot of tokens isn't enough. I mean, you think kernel.org folks haven't put some serious thought into it? And yet, as HN argues about it, there's kernel.org running anubis at difficulty 5.

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tptacek 4 hours ago | parent [-]

I don't know what you mean by "the best argument". My entire argument is that it's bad CS. I'm not trying to convince people not to run Anubis. If anything, I'm trying to convince Anubis to use better computer science. That would make more people run it! But even that's just a faint subsidiary goal; the real goal, as someone who works in this field and has designed proof-of-work antiabuse systems before, is just to add clarity about what can and can't work and why.

	▲	harshreality 4 hours ago \| parent [-]
		I too would love anubis to use better CS, if available. Perhaps you have some ideas for @xena, instead of just letting anubis continue on the trajectory of iterating its PoW approach?

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inigyou 2 hours ago | parent | prev [-]

Which part of computer science is about getting DDoSed by billionaires who are above the law?

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TeMPOraL 2 hours ago | parent [-]

Where on Earth do people get the belief that:

- It's the SOTA companies doing it?

- Scrapers are doing it for training data?

Those are two assumptions I see in posts and threads around Anubis, that are taken at faith, and never once substantiated.

	▲	inigyou 2 hours ago \| parent [-]
		What's your alternative hypothesis?

▲ nneonneo 6 hours ago | parent | prev [-]

I disagree. The kernel finds it effective - 66% of scrapers are turned away directly.

The scraper problem now is fleets of residential proxy devices - often things like smart TVs, phones, and browsers with some “proxy SDK” installed as part of an app’s monetization scheme. They make a couple of requests to a site - just enough to fly under the radar - and move on to a different site.

If each new site they hit forces them to solve a proof-of-work, that’s a meaningful dent in their scraping performance. Many of these boxes may not even have the spare CPU power to efficiently solve so many proofs of work - and anything that makes an owner notice their device is running slow is something that could meaningfully impede adoption of these SDKs, or force the operators to choose between minimizing performance impact or scraping more sites.

▲ tptacek 6 hours ago | parent | next [-]

It's weird to believe data center based, Internet-scale scraping operations will be less able to allocate compute to proof-of-work challenges than individual users. This is design problem with things like Anubis: proof-of-work depends on a cost asymmetry between attacker and defender. But in scraping, both legitimate users and scrapers get the same value out of a transaction.

	▲	yorwba 2 hours ago \| parent \| next [-]
		For PoW to work, you don't need scrapers to have less compute than users, you only need their compute advantage to be less than the load-generation advantage they would otherwise have. And unlike legitimate users, scrapers aren't carefully picking the URLs they request, so the average value they get out of it is probably rather low. They have to make it up in volume.
	▲	6 hours ago \| parent \| prev [-]
		[deleted]

▲ Y_Y 6 hours ago | parent | prev | next [-]

The implication here is that the proxy fridge forwards the Anubis challenge to a dedicated rig controlled by the scraper who efficiently solves it and returns the answer.

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wongarsu 4 hours ago | parent [-]

That's still a notable step up in completely and resource investment for the crawler

See also how captchas continued being effective for years despite services like anti-captcha offering to solve them for you for a fifth of a cent each by farming the work out to India. It took advances in AI that made it viable to reliably solve them on-device to bring the end of the captcha

	▲	inigyou 2 hours ago \| parent [-]
		That's not a step up, that is how they work by default.

▲ lxgr 5 hours ago | parent | prev | next [-]

Why would they even run a browser engine on the devices they're hosted on?

All they need to do is forward traffic and launder its IP origin. They don't even need to be able to (and would actually be well advised not to) decrypt TLS streams.

▲ oasisbob 4 hours ago | parent | prev | next [-]

> Many of these boxes may not even have the spare CPU power ...

I don't think that's generally how these networks use residential exit proxies. There are at least a dozen well-developed frameworks out there for decoupling the crawler from the network exit point.

Most res proxy exits are just slinging bytes for clients using SOCKS, or another tunneling protocol.

If nothing else, a modern scraper will want better control over their TLS fingerprints, and you can't get that if you're depending on the on-device TLS libraries alone.

▲ lxgr 5 hours ago | parent | prev | next [-]

> 66% of scrapers are turned away directly.

Until they discover this neat trick [1] and solve challenges orders of magnitudes more efficiently than legitimate users.

The game theory of Anubis is not sound. It makes fundamentally less sense than Captchas, and even those have been on the way out for a while.

[1] https://news.ycombinator.com/item?id=49500040

▲ semiquaver 4 hours ago | parent | prev | next [-]

  > meaningful dent

Until you actually do the math and realize that it is not meaningful at all. It’s equivalent to the blogs that have a custom “bot protector” that asks you “what’s 2+2” every time you submit a comment. It might work temporarily as an inconvenience, but nothing more.

▲ graemep 5 hours ago | parent | prev [-]

How s that measured? How do you count human users who have been turned away?