Why are anime catgirls blocking my access to the Linux kernel?

Summary

Hey… quick question, why are anime catgirls blocking my access to the Linux kernel? Intro I’ve started running into more sites recently that deploy Anubis, a sort of hybrid art project slash network countermeasure. The project “weighs the souls” of HTTP requests to help protect the web from AI crawlers. If you’ve seen anime catgirl avatars when visiting a new website, that’s Anubis. A website blocked with Anubis I’m sympathetic to the cause – I host this blog on a single core 128MB VPS, I can tell you some stories about aggressive crawlers! Anubis recently started blocking how I access git.kernel.org and lore.kernel.org. Those sites host the Linux Kernel Mailing List archive and the kernel git repositories. As far as I know I do have a soul, I just wasn’t using a desktop browser… so how exactly is my soul being weighed? Note: Linux has Tux 🐧, OpenBSD has Puffy 🐡, SuSE has Geeko 🦎 and Microsoft has Bob 🤓… nothing wrong with mascots! 😸 Problem The traditional solution to blocking nuisance crawlers is to use a combination of rate limiting and CAPTCHAs. The CAPTCHA forces vistors to solve a problem designed to be very difficult for computers but trivial for humans. This isn’t perfect of course, we can debate the accessibility tradeoffs and weaknesses, but conceptually the idea makes some sense. Anubis – confusingly – inverts this idea. It insists visitors solve a problem trivial for computers, but impossible for humans. Visitors are asked to brute force a value that when appended to a challenge string, causes it’s SHA-256 to begin with a few zero nibbles. calcString := fmt.Sprintf("%s%d", challenge, nonce) calculated := internal.SHA256sum(calcString) if subtle.ConstantTimeCompare([]byte(response), []byte(calculated)) != 1 { // ... } // compare the leading zeroes if !strings.HasPrefix(response, strings.Repeat("0", rule.Challenge.Difficulty)) { // ... } source: lib/challenge/proofofwork/proofofwork.go#L66 If that sounds familiar, it’s because it’s similar to how bitcoin m...