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Javascript that auto-fills captchas
- skorgu 18y agoThere's a static demo at http://herecomethelizards.co.uk/mu_captcha/ http://herecomethelizards.co.uk/mu_captcha/ (via reddit comment)
- geuis 18y agoThe OCR thing is definitely interesting. But what I find more compelling is that the author created a simple neural network in javascript. Rock!
- rarrrrrr 18y agoThis is exactly why when we wrote the CAPTCHA code that protects the creation of SpiderOak 2gb free backup accounts (well commented GPLv3 code here -- https://spideroak.com/code https://spideroak.com/code ) we took the approach of not making them 100% human readable. Supposedly it greatly increases the cracking difficulty at the relatively small expense that humans may have to click Next a small percentage of the time. If we notice abuse, it will be easy to tweak the code (it's just a python gimp script) to produce a radically different captcha for a few hours work.
- DavidPP 18y agoLast week, I was going to register a new web service (forgot which one) and after the third captcha I couldn't get right, I just quit and decided to use a competitor instead. What I'm trying to say is that ideally you shouldn't use a solution that is less user friendly and possibly infuriating for your future customers/users.
- rarrrrrr 18y agoIndeed. It's a balance. Three failures is way too hard. Ours is a fairly simple captcha -- 5 letters/numbers, and our logs show that somewhere around 94% of attempts are correct, and we see few abandoned signups during the captcha answering phase. We could probably improve that further, though. The primary defense against OCR is to make the segmentation attack hard -- pushing the characters together somewhat. With more tweaking we could probably get closer to a sweet spot of just enough overlap. Not even all of the characters would have to overlap to be effective.
- axod 18y agoBut it's a moot point, since anyone who really wants to defeat captchas en masse, can just go mechanical turk, or even better just setup their own 'porn/warez' sites etc to show your captchas and have random internet users solve it for them. There's no defense against that... Which makes captchas just a big irritating bag of fail.
- irrelative 18y agoIndeed! In my experience, the best captcha is asking for a credit card number.
- cdr 18y agoIn the same vein, the best captcha is not letting anyone sign up at all.
- rarrrrrr 18y agoI think of it as similar to a home security system. Of course there are ways around it. Chances are that the effort involved means that a burglar will go rob a neighbor's house instead though. Perhaps captchas make more sense in capital intensive industries with clear avenues for abuse. In the case of SpiderOak, we'd prefer to avoid making the free backup accounts an attractive prospect for warez distribution. YMMV.
- apollo 18y agoAre you sure you're human?
- jonursenbach 18y agoI for one, welcome our CAPTCHA-weilding overlords.
- zain 18y agowe took the approach of not making them 100% human readable. Sounds like a great way to make sure neither bots nor humans use your service.
- rarrrrrr 18y ago"It ain't so much the things we don't know that get us into trouble. It's the things we know that just ain't so." Like everything else about building software, you have to test it. Watch the logs and see where people abandon the process. If it's a problem, fix it.
- eli 18y agoI don't follow. Even the best spam bots don't solve every CAPTCHA. If it's a miss (either because they got it wrong or because it's actually unsolvable), they'll just try again, no? I would think actual humans have time that is more valuable than zombified Windows boxes.
- medearis 18y agoIt really doesn't look to me like megaupload worked too hard on their captcha. In the general case, this is apparently a difficult problem because of the character segmentation step. So, my guess is that if megaupload did something to decrease the distinction between characters (script letters, for example), the feasibility of a javascript implementation would break down.
- tlrobinson 18y agoImagine how much power Google could harness if they just put a little JavaScript that did some parallelizable task on google.com. Since it's so many people's default page, at any given time there's probably millions of computers idling with it open. If I were Google I would be sooo evil.
- eli 18y agoI wrote a userscript to auto-fill the text-based CAPTCHAs that Drupal.org was using for a while. That was just some regexp fun. This is a bit more impressive.
- statictype 18y agoWait - you parsed an image using regexes? Or is it something else?
- eli 18y agoSorry, should have been clear. They were text-based of the form "which of these does not belong?"
- seldo 18y agoWOW is this going to piss of a lot of website owners who rely on captchas. If you can do this in Javascript, then you can do it much better in a server-side language and hook it to the front of your spam cannon. Boo to the spam arms race getting another degree more vicious.
- statictype 18y agoHere's an idea I've seen implemented in some captchas: Instead of generating an image of text that most people have to strain to read, instead, generate a relatively cleaner image but instead of typing that in, have it ask a question to be answered. "What do you get when you add 2 and 2?" etc... Would that fare better?
- gravitycop 18y agoThat is an IQ test. It fails to reliably differentiate between machines and humans, as machines become human.
- Zev 18y agoWhat about people that type in "four" or "IV" instead of the expected numeral "4"? The answer is still technically correct but one fails the catchpa.
- est 18y agoI've seen those stupid mathematics captcha, there's a thing called eval() in javascript.
- eli 18y agoJohn Resig did a writeup on how it works (and the author makes an appearance in the comments): http://ejohn.org/blog/ocr-and-neural-nets-in-javascript/ http://ejohn.org/blog/ocr-and-neural-nets-in-javascript/
- Prabhu 17y agohow to segment the captcha's text