CAPTCHAs can still detect AI agents (opens in new tab)

I had to do a Captcha the other day, and the letters looked awful, so I clicked the speaker for an audible Captcha instead. I was even more horrified. The sound was almost painful. Sharp noise blasting as a high pitched tinny voice bellowed numbers at me. I honestly don't know how blind people use the internet these days with such blockers in place, and that's kind of sad. The cookie banners, the captchas and the bots and laws that made both appear have kinda en$hittified humanity's greatest communication tool.

CAPTCHAs are great. Exploiters get around them with proprietary anti-detect browsers and unethical residential proxies, while privacy browsers and affordable privacy VPNs get blocked and shadowbanned to death.

Fingerprint.com, while not a CAPTCHA, gives you +3 suspicious score just for using privacy settings like adblock on your browser. This makes it harder to sign up for any sites that use fingerprint.com.

https://github.com/CloakHQ/CloakBrowser is a good anti-detect browser as well as CAPTCHA bypass which is honestly fun to use coming from privacy browsers because every site just works and captchas get solved.

Captchas are primarily to punish users for not allowing tracking, or using the “right” services, they may prevent some bots as a side effect (or a pretence from the provider) but it’s mostly for google and cloudflare to abuse their monopolies.

This feels like the kind of thing where, "you must be at least this human to pass" and that it just otherwise mostly wastes your time if you're a robot would cover most of what Captchas are useful for.

Like, if it takes you 3-5 seconds to get through a captcha as a human, as long as every single event has that effort added, the impact to something trying to use/reuse the end-page is way worse if you're a robot than if you're a human.

I can see a few usecases where it would still be valuable to continue the game of cat-and-mouse, but I feel like solving for consistency of human experience of your website, may actually be more punishing to anything trying to bypass it.

But.. the task was never "detect this" but always "detect this within acceptable constraints".

Sure, once you collect enough bits, you can tell that its me. And if you know from other sources that I am human, that solves your immediate problem. But if you do that, you have still failed at the task of detecting certain kind of abusive behavior without harming my anonymity.

Appreciate this article...shows some interesting insights on how humans "behave" vs agents.

Apparently CloudFlare’s turnstile can’t, as evidenced by several public-facing CRUD and mail routines we maintain that no longer are warding off the spam.

I think it's just a game of cat and mouse. It might be easier to catch naive AI agents that are not fine-tuned for specific CAPTCHA tasks with human behavior, can't recognize new challenges, don't know when to stop and ask a human, and just want to brute force their way with limited or no specialized harness and tools available.

- LLMs can't learn, therefore, LLMs are only good for things on which they are trained. - Captchas are not friendly with trial and error, so agentic solutions also don't help. - It's impractical to train LLMs on everything. - We humans are capable of creating infinite ways of captchas.

While each of these sentences is true, captchas will always win against LLMs.

So now I have to fail the capcha to prove I'm human, but in the right way? We don't hate these people enough.

Adversaries do not have to wait for LLM models to evolve to mimic human process, they can simply evade the detection JavaScript that evaluates similarity. JavaScript is visible, can easily be reverse-engineered.

I’ve been using Claude Opus 4.7 with Chrome MCP, and it has worked successfully about 95% of the time. However, I’ve failed various hCaptcha challenges.

What happened to adversarial attacks? I.e. noise that makes an image look like something else to a classifier than to humans. I guess frontier LLMs are no longer vulnerable to those?

Until they learn to do that. So cat and mouse. So nothing new.