Forgot your password?
typodupeerror
The Internet Books Media Technology

Fill Out CAPTCHAs, Digitize Books At The Same Time 121

Posted by Zonk
from the i-would-like-to-subscribe-to-your-newsletter dept.
alphadogg wrote with a link to a Networld article about a noble endeavor: putting CAPTCHAs to work for the good of humanity. A scientist at Carnegie Mellon is looking to create a new type of security check that will assist in a project meant to digitize and make searchable text from books and printed materials. Above and beyond that, the offering would probably be more secure than most current systems. "Instead of requiring visitors to retype random numbers and letters, they would retype text that otherwise is difficult for the optical character recognition systems to decipher when being used to digitize books and other printed materials. The translated text would then go toward the digitization of the printed material on behalf of the Internet Archive project."
This discussion has been archived. No new comments can be posted.

Fill Out CAPTCHAs, Digitize Books At The Same Time

Comments Filter:
  • Verification? (Score:5, Insightful)

    by traindirector (1001483) * on Thursday May 24, 2007 @06:16PM (#19262111)

    CAPTCHAs work because the computers sending them already know what the text says; they start with it in text form and change it into a hard-to-read image. In the system discussed in the article, how will the computer verify that the user response actually matches the text? Sure, it could compare the response to its best guess, but if a program trying to guess the text was equally as sophisicated as the guessing computer, the guess would match.

    I imagine the computer sending the picture of the image of hard-to-read text will further obfuscate the image in a way that makes it even more difficult for the computer on the receiving end to decipher, but the article doesn't acknowledge that this is one of the first logical questions in conceiving of / implementing this system in a functional way. The article really should cover this...

    • Re:Verification? (Score:5, Informative)

      by greatgregg (1106739) on Thursday May 24, 2007 @06:19PM (#19262153)
      From recaptcha.net [recaptcha.net]: "But if a computer can't read such a CAPTCHA, how does the system know the correct answer to the puzzle? Here's how: Each new word that cannot be read correctly by OCR is given to a user in conjunction with another word for which the answer is already known. The user is then asked to read both words. If they solve the one for which the answer is known, the system assumes their answer is correct for the new one. The system then gives the new image to a number of other people to determine, with higher confidence, whether the original answer was correct."
      • by traindirector (1001483) * on Thursday May 24, 2007 @06:23PM (#19262213)

        I originally missed the link to the official site - D'oh. The article also doesn't mention that the system is already in use! http://recaptcha.net/ [recaptcha.net]

        • by caffeinemessiah (918089) on Thursday May 24, 2007 @07:46PM (#19263215) Journal
          There's an interesting solution to this problem -- the "scientist at Carnegie Mellon" is Luis von Ahn [cmu.edu] who was recently awarded a MacArthur genius award. In optical recognition tasks like this where the "true" answer is not known, how do you verify that a human agent correctly did the recognition? Just see if a bunch of other users type the same thing. It's a clever twist on consensus voting, and was recently snatched up by Google as "Google image labeler" here [google.com].
          • Re: (Score:3, Interesting)

            by MindStalker (22827)
            Problem is, for the first few people seeing a new Capatcha the computer will have to let you through even if you guess wrong, so the lock feature of the Capatcha doesn't work.

            As others mentioned this system gives you a known then an unknown, though I think its stupid that it further makes it difficult by putting a slash through it and making it wavey. Helloo, if you system had a hard time recognizing it why do you want to make it harder to recognize. I saw several in the examples in which the word was nonen
            • No, because the "lock" feature of the captcha isn't the word that is being digitised, it is an unmodified run-of-the-mill captcha (GPP). This merely adds a little bit of work for the user (and I'm assuming once the mystery word has been verified by consensus, they'd begin to exclusively use the mystery word). They may even just take the mystery word in the original text (the one being digitised) and couple it with the one before/after that *WAS* translatable, but was then captcha-tised for regular captcha u
            • by rholliday (754515)

              There needs to be a I don't know button as well :)
              There is. If you take another look [recaptcha.net] you'll note there's a button to reload it and get a new one, as well as one to get an audio challenge.
          • There's an interesting solution to this problem -- the "scientist at Carnegie Mellon" is Luis von Ahn [cmu.edu] who was recently awarded a MacArthur genius award. In optical recognition tasks like this where the "true" answer is not known, how do you verify that a human agent correctly did the recognition? Just see if a bunch of other users type the same thing. It's a clever twist on consensus voting, and was recently snatched up by Google as "Google image labeler" here [google.com].

            it was also previously available as The ESP Game [espgame.org], from...(wait for it)...Carnegie Mellon

          • by maaskaas (1103983)
            There is a Google Techtalk with "this scientist" available here: http://video.google.com/videoplay?docid=-824646398 0976635143 [google.com]. This way of using simple techniques are so innovative, because it can perform really complex tasks that no one thought about before. Some of his other projects include online "games" (Peek a boom) which collects relevant data from the users playing it so that a computer can determine what kind of object is in a digital picture, and where it is located. It is really a big step for
          • See, for recognizing words, that's ok. You can give it to 200 users spread over 10 days and see what most said. So, yes, I'm not surprised that Google does the same thing, but the catch is: not as a captcha.

            It's just about the most idiotic idea I've ever heard for a _CAPTCHA_. Here's why:

            1. What about the first person that sees any given word? Do you let them get in regardless of what they type (remember, there is no consensus yet about that word)? Or will I have to wait another 2 weeks to see if my post is
            • You raise some good points, anyway if a weight is given to the submitted answers according to its string similarity with the ocr (wrong) guess and a dictionary, then it becomes easier to spot spammers, unless spammers do an ocr and post the second best dictionary guess. Anyway, no "goatse" instead of "slashdot". Add that to the captcha server being centralized so bots can be analysed for submission and/or error frequency and demoted or given "impossible" captchas.
              • As you probably noticed, my 3'rd objection was, essentially, "but spammers could run it through an OCR and then guess at the 1-2 misshapen letters". So you're telling me that then the system would do the same to validate that you're not a bot.

                I dunno... it seems to me that, au contraire, you just described a way to make it easier for bots to pass. Magna cum laude.

                You even have the exact way to tune it for maximum effect: the guys with the same OCR software are more likely to pass. Even if you don't exactly
                • But they don't have the same data of the "captcha server" to do ocr, they have the distorted one. The similarity is weighed with the original data, so bots ought to have a pretty good ocr program, equivalent to a pretty good captcha decoder.
            • Uhh, you seem to be stuck on the idea that they only use the mystery word for captcha.
              Maybe you should actually read the comments you replied to...which quote the reCAPTCHA website:

              But if a computer can't read such a CAPTCHA, how does the system know the correct answer to the puzzle? Here's how: Each new word that cannot be read correctly by OCR is given to a user in conjunction with another word for which the answer is already known. The user is then asked to read both words. If they solve the one for wh

          • by neongrau (1032968)
            ok, so they "ripped off" the concept of /. meta moderation ;)

            sue them!

            j/k
          • by evilviper (135110)

            how do you verify that a human agent correctly did the recognition? Just see if a bunch of other users type the same thing.

            I'm not going to type in a captcha and just wait around on the page for an hour until X other people try to answer it... This system of yours gives priority to the answers of the first few people that see it, which may well be the OCR system of some spammers.

            Even more, once you've got the first few answers, then it's just a typical captcha, as you already have had it entered, and know

          • by GeneJoker (549689)
            So I take a try and google image label, and the SECOND GODDAMN PICTURE was furry porn.
            I hate you internet.
            (I'm sorry I didn't mean it we'll never fight again)
      • Re: (Score:2, Informative)

        by nwbvt (768631)

        Considering all the other people who asked that question, they really needed to make that clear in their press releases.

        So if you want to screw with it, all you have to do is intentionally get exactly one word wrong each time. Yeah, it will often take two tries to get it right, but its not like CAPTCHAs usually work fine on one try anyways... And hey, if you just try for only one word (and leave the other blank), you will end up on average typing the same amount.

        The article makes comparisons to SETI@H

        • Re:Verification? (Score:5, Insightful)

          by Falkkin (97268) on Thursday May 24, 2007 @07:00PM (#19262635) Homepage
          "So if you want to screw with it, all you have to do is intentionally get exactly one word wrong each time."

          Well... sort of. Multiple agreements are required before the system will accept that it knows the spelling of a previously unknown word. So you're not going to singlehandedly subvert the system; at the very least you need a cabal of friends. But with millions of words available in the system, the chance that you and a bunch of friends will all get the same word and write in the same bogus data is pretty close to zero. I'm not saying it this system is impossible to game, but I think it'd be heck of a lot easier (and more rewarding, if it's the sort of thing that floats your boat) to vandalize Wikipedia instead.
          • by nwbvt (768631)

            It doesn't need to be planned. For instance if the given text is very close to something dirty, a lot of people will get the same idea and will put in the same text. And if you doubt the power pranksters like this can have, look back at the Google bombing episodes.

            The Wikipedia is a bit different as you have to make an effort here. People are not required to write Wikipedia articles to sign up for an email account or post on a message board. If they were, the resulting information would be even less c

      • by bugnuts (94678) on Thursday May 24, 2007 @06:48PM (#19262503) Journal
        The problem is that any unsophisticated captcha interpreter can spit out the text that's known, and make a (bad) guess at what is hard to read. Then, if there is any significant amount of spammers, we end up with exactly the same issue - computers having trouble with OCR.

        e.g., /. puts in a captcha to translate the following two sections:
        12345
        l1il1

        The captcha software knows the "12345"
        but it doesn't know the "l1ill1". A human could figure out both.

        But spammer captcha deciphering can figure out 12345, and is allowed to incorrectly guess 11ii1 for the 2nd part. End result is
        • a spammer is posting something as indecipherable as this message except insults your penis size
        • some OCRed book is now committed to a false interpretation
        • I have to change the password on my luggage.

        • Re:Verification? (Score:5, Insightful)

          by Bjarke Roune (107212) on Thursday May 24, 2007 @06:59PM (#19262627) Homepage
          This is not a problem if the known word is a hard image that has been solved by humans in previous captchas. This scheme works as long as the system has a small pool of known images to start the process off.
        • Re:Verification? (Score:4, Informative)

          by autophile (640621) on Thursday May 24, 2007 @07:25PM (#19262959)

          Yeah, but it's not like you're only allowed to present a given unknown word once. Present it many times, and use the word with the most hits.

          --Rob

          • it's not like you're only allowed to present a given unknown word once. Present it many times, and use the word with the most hits.

            True. But captchas generally require prompt feedback; you want to know right away whether or not the user has passed the Turing test, not leave it unknown for a couple hours until a sufficient number of other users have submitted their answers to establish a consensus.
            • That's why you use the first word (also a digitized word, but one that has been verified by the technique) for the turning test, and the second word to extend the turning test vocabulary.
      • Re: (Score:3, Interesting)

        This is one of the most creative ideas I've heard all year. Human-based distributed computing with captchas? Awesome!
      • by jambarama (784670)
        That sounds fine, but I'd still be worried about the accuracy of the read. As long as we're going to have users read and answer two captchas, why don't do this: present the unknown captcha to two people, if they agree on the answer accept it, if not show the same captcha to a third person. Accuracy is probably more important than speed for books that still haven't been digitized.
        • Re: (Score:2, Insightful)

          by poopdeville (841677)
          Because nobody wants to wait around for another person to verify the CAPTCHA before posting on /. That is, you need two CAPTCHA images because you still want them to work as a CAPTCHA.
          • Why not have the CAPTCHA look something like this: (use K for a known character and U for an unknown character)
            KUKUKUK (or some other random permutation of K & U in the desired length)

            This way, you can
            a) check all the K's for validitity, if so, then ACCEPT
            b) Break up words so that they aren't as easily recognizeable
            c) Still allows you to compare different people's answers for U's, as you aren't using them for validity
            d) I would think that this method would reduce the number of "Jackasses" because you ne
        • by Endo13 (1000782)
          Um... did you even read all of the post you're replying to?

          The system then gives the new image to a number of other people to determine, with higher confidence, whether the original answer was correct.
          That sounds like a pretty good system to me.

          You do realize that "a number of other people" here could refer to even several dozen or several hundred?

          So clearly it's not going to be just one person that determines the answer for unknown captchas.
      • by Bluedove (93417)
        it's even easier than that. the same captcha [wikipedia.org] gets presented randomly to two people (quasi-)simultaneously. Unless both parties type the same word, neither is verified. This gives an added incentive to people to type what it really says. Of course, it leaves open some room for the sub-class of assholes who will gleefully spend hours typing the wrong answer to captcha [wikipedia.org]s, just to fsck with the other guy. That's why you always have to give a failed verification a couple of chances. Hey, sometimes i mistype
    • by mikee805 (1091195)
      I read the article trying to find an answer that. This system works for what they want. Get disrupted OCR done by humans, but does not seem to preform the job of a CAPTCHA.
    • Re: (Score:1, Redundant)

      by 26199 (577806) *

      That was my thought. I suppose you could let the first five people through automatically, then use their answers to check everyone else; but what's the point of a CAPTCHA that lets a certain minimum portion through?

      Turning people away when they actually got it right is worse, though; that way you potentially lose customers in trying to fight spam.

      Seems like an interesting idea, but I don't see how it can work...

      • by 26199 (577806)

        And poster above has explained nicely how it works. Thanks. They could have put that in the article... (or summary!)

    • Yea that doesn't quite seem to make sense. I can only see this leading to poor transcriptions with no security benefit.
    • What you said. Also, register-bots will destroy this because their OCR will come up with something close to what the serving computer already knows. And it'll put in incorrect results, which will pass security AND be added to the digital book, and now your precious digital book has more OCR typos than it would have in the first place.
      • Re: (Score:2, Informative)

        http://recaptcha.net/security.html [recaptcha.net] the words are additionally distorted and they add lines and warps so that a computer cannot read it.
      • by delinear (991444)
        As the other poster stated, the image is distorted so that standard OCR technology won't be able to make a very good guess with any certainty. Additionally I think a double-blind is used, where two words are displayed, one the system knows in advanced and one it doesn't. The OCR would have to get the first one exactly correct in order to distort the results of the second one (since if the first verification check is failed the suggested word is discarded completely and ha no skewing effects on results). If
    • The article states:

      "I think it's a brilliant idea -- using the Internet to correct OCR mistakes,"

      Suggesting that the words have been OCR'd, and that the user is correct the mistakes. This goes on to suggest that there is a margin of error that takes into account OCR mistakes but will allow the corrected text.

      With a little imagination, it's easy to think of many permutations to this, along with the idea of just asking for a new captcha if the first one doesn't work.

      The article also states there's a speakabl
    • They need a way to verify if the answer is correct... if they know the answer, they don't need help digitizing the hard-to-read text. If they don't know the answer, it won't work as a CAPTCHA.

      Am I missing something fundamental here?
      • by Falkkin (97268) on Thursday May 24, 2007 @06:29PM (#19262293) Homepage
        The system serves two words to the user. The system knows the correct answer to one of these words -- this is the one used to test whether the user is a human or a bot. If the user got the test word right, then there's a good chance they also got the unknown word right. If a bunch of humans all agree on the same transcription of a given unknown word, the system will eventually "know" the correct spelling of the unknown word and can then serve it as a "known" word in the future.
        • by hpavc (129350) on Thursday May 24, 2007 @07:17PM (#19262869)
          Likely has a good idea on 'unknown' word as well, the example "This aged portion of society were distinguished from" the OCR didn't cut it but it did did kick start a guess. At least on "This -> niis" it can see its not 'ZOMG' or 'Fark' easy enough.

          Also it wouldn't take much to add some grammar to pad the guessing. While we wee two words the system sees them in at least two contexts.

          Obviously it has the actual dictionary to help it basically spell check the words we submit to it. If the words we give it are completely garbage, its unlikely to go for it. Which is where knowing that "niis" needs a correction.
      • It isn't being used as a captcha. It is being disguised as a captcha in order to get a person to translate:

        Computer: [unreadable scribble]
        User: Bartholomew
        Computer: Please try again.
        [Captcha image]

        User:Red49
        Computer: Access Granted!
        Computer to OCR Central: [unreadable scribble]="Bartholomew"
    • from the website :: http://recaptcha.net/learnmore.html [recaptcha.net]

      "But if a computer can't read such a CAPTCHA, how does the system know the correct answer to the puzzle? Here's how: Each new word that cannot be read correctly by OCR is given to a user in conjunction with another word for which the answer is already known. The user is then asked to read both words. If they solve the one for which the answer is known, the system assumes their answer is correct for the new one. The system then gives the new image to a

    • by alstor (587931)
      I had the exact same thoughts when I skimmed the article...
    • They probably just accept the first x entries until they have a base for comparison. The entries will converge on correctness.
    • Re: (Score:2, Informative)

      by DeathElk (883654)
      RTFA's TFA
    • In a hole in the ground there lived a penis. Not a nasty, dirty, wet hole, filled with the ends of worms and an oozy smell, nor yet a dry, bare, sandy hole with nothing in it to sit down on or to eat: it was a hobbit-hole, and that means comfort.

      (yeah, i'd trust the internet community to digitize my books. why don't we just cut out the middle-man, and create a wiki-gutenberg project?)

  • Better links (Score:5, Informative)

    by Falkkin (97268) on Thursday May 24, 2007 @06:21PM (#19262165) Homepage
    The article is lacking some information. Here are some better links:

    Official reCAPTCHA site [recaptcha.net]
    Hide your email address with reCAPTCHA [recaptcha.net] (super easy!)
    A more detailed blog post about how the system works [blogspot.com]

    Disclaimer: I work with Luis von Ahn [cmu.edu], who's the professor running the reCAPTCHA project.
    • Re:Better links (Score:5, Interesting)

      by inKubus (199753) on Thursday May 24, 2007 @06:54PM (#19262567) Homepage Journal
      Also, Amazon has a pretty cool program [mturk.com] where you can perform HITs (Human Intelligence Tasks) for a few cents each. They have a lot of stuff like transcribing podcasts, identifying stuff in satellite images, etc.
      • by JonathanR (852748)

        identifying stuff in satellite images, etc.
        I hope George Tenet is not the director of that business unit...
      • HITs (Human Intelligence Tasks) for a few cents each


        Brings to mind a dystopian (and fictional) future where robots lord it over us but still need us to process large amounts of data for them. Like the Matrix, but without violating the laws of Thermodynamics. That'd make a cool SF novel, I think...
  • someone set up a database of what the words really say along with what we should type instead, and make it public. it'll be fun! like mad libs!
    • by Kaetemi (928767)
      Apparently it seems to be having some trouble with seeing the difference between "which" and "witch" ^^
  • by penguinbroker (1000903) on Thursday May 24, 2007 @06:37PM (#19262397)
    This would also be a great approach to a lot of NLP/Translation annotation tasks. Although these types of tasks generally require a robustness (knowing which answers to trust and which to ignore) that anonymity makes difficult.

    http://yro.slashdot.org/article.pl?sid=07/04/03/22 11258 [slashdot.org]

    I believe amazon.com has filed a patent for a solution to this problem which attributes every annotation input to a unique user id. They then claim to use the average accuracy over the history of that user for whittling away the, 2 out of 10 i think the patent says, worst answers.

    i'm sure some form of quality control/check will be needed and i wonder if such a solution would infringe on this patent?

    • by Chysn (898420)
      > This would also be a great approach to a lot of NLP/Translation annotation tasks.

      This would also be a great approach to solving captchas on other sites. Wanna buy tickets with a bot but have a captcha in your way? Set up a third-party captcha server to have humans solve your captchas for you!
  • Booger (Score:2, Insightful)

    by Tablizer (95088)
    What if the OCR cannot read a word because there was a booger on it during the scan? A human won't be able to determine it either because it will be mostly a blotch. How are they gonna know the difference between human-decipherable words and lost-cause words (such as booger blotches)?
    • they could offer a button that states : "this is not text" and then the user would be given a whole new captcha
      • by Tablizer (95088)
        they could offer a button that states : "this is not text" and then the user would be given a whole new captcha

        But then a bot may exploit it by passing on until it finds one it can process.
                 
        • a lot of login boxes have a system of recording successive requests from an ip address to stop brute force login hacks. a similar method could be used here.
  • How it could work (Score:3, Insightful)

    by AaronW (33736) on Thursday May 24, 2007 @06:45PM (#19262465) Homepage
    I can see how this would work, but in order to also provide security, extra letters or words would also need to be in the captcha. I.e. if there's an un-OCRable word "between", the captcha could contain "frog between" or something like that, and the first word could be a previous un-OCRable word that has been validated by enough people.

    Another method might be to separate out the un-OCRable letters from words and sprinkle them with known letters, though this might be less effective since people can often recognize words far better than individual letters. If one or two letters in a word cannot be interpreted, a person can often still read the entire word.
  • Spammers are already using CAPTCHA techniques to automate account creations on protected websites:
    1. Have a person subscribe to a porn website by typing in a CAPTCHA image that comes from a legitimate website.
    2. The user provides the correct word while subscribing
    3. Not even a "???" step
    4. Profit! The protected website is spammed.
    I'm wondering whether this system will be used for legitimate OCR purposes or for more spam...
    • by Falkkin (97268)
      CAPTCHAs simply tell whether there's a person sitting at the other end of the machine. No CAPTCHA can tell you whether that person is a malicious user or not. With this approach, at least the spammers are helping to digitize books.
    • by 1u3hr (530656)
      Spammers are already using CAPTCHA techniques to automate account creations on protected websites

      Really? How do you know this? Can you give an example of a porn site that asks for captchas? If not, it's an urban legend.

      I've seen this suggested as an attack on captchas, but never heard of any site that put it into practice. Probably it is simpler to pay some third-world computer sweatshop worker to solve hundreds of them per hour for a few dollars a day. But that's equally a conjecture.

      Dodgy free porn s

  • A better scheme would be to give out the same capcha to 2 or more users. If they agree on the answer, then there's a better chance that the text is correct.
    • Re: (Score:2, Informative)

      by tepples (727027)

      A better scheme would be to give out the same capcha to 2 or more users. If they agree on the answer, then there's a better chance that the text is correct.
      The Article states that the system already does this.
  • ...Wait till you see these new CAPTCHAS.

    Mushed text with letters that slide into each other, bad lighting and every other kind of bad scanning you can imagine. Hell, you'd be lucky if you can recognize letters at all.

    Question is, if the machine couldn't figure out what the word is, how will it verify your answer? Is it going to be something along "by the popular vote"?

    Something is very not right in all this.
  • A pain for users (Score:2, Insightful)

    by EssenceLumin (755374)
    Great, so now I would have to fill out two of those stupid things instead of one. Why would a company want to inflict this on its users?
    • Poor you! Now, every other week where you'll want to join a new forum (that's a LOT of forums), you'll have to solve two CAPTCHAs instead of one! Waaaaaah!
      • Oh whatever. When I do want to join a site they sometimes have captchas that I can't figure out and have to try five of them or however many. It's frustrating. Throw in a second one which was put there because it is illegible and I'll say oh well, forget it. Forums aren't the only places using them either.
    • by Falkkin (97268)
      I think it's faster for me to process and type two English words than to type one word that's just random letters. My brain is trained to read and type English; it's not trained to type nonsense.
  • by Joebert (946227)
    Please type the characters you see in the following image to register.

    George Bush

    Type: Miserable Failure

    Thankyou, click here to proceed.
  • This project isn't the first of its sort: Amazon has the Mechanical Turk project, where users perform various tasks similar to CAPTCHAs for amazon.com credit.

    http://www.mturk.com/ [mturk.com]
  • So, let me get this straight. There are systems out there, in the wild so to speak, that offer security by presenting a task that humans can do easily but machines have trouble doing. And now, this very same system is going to assist machines in solving the very inability upon which the system is based.

    That's the dumbest most retarded (traditional sense of teh word) thing that I've ever heard.
  • From the security page of the reCAPTCHA site [recaptcha.net]: "if somebody writes a program that can read our distorted images, we can add more distortions in very little time"

    If someone can write a program to solve the distorted images of OCR-unreadable words, don't you just hire that guy to do your OCR and get out of the CAPTCHA business?
  • Image spam (Score:5, Interesting)

    by JeremyR (6924) on Thursday May 24, 2007 @11:12PM (#19265151) Homepage
    Maybe this technique can be adapted to fight image spam more effectively :-)
  • CAPTCHA+CAPTCHA (Score:1, Redundant)

    by k3vlar (979024)
    I thought the point of CAPTCHAs was to compare what a user types with information stored on the hosting server. If the hosting server doesn't know what the book says, then how can it validate the CAPTCHA?
  • by WiseWeasel (92224) on Friday May 25, 2007 @03:35AM (#19266963)
    Damnit, where's the smushed bug key?!?
  • The second request is by definition not a CAPTCHA, since the answer is not known. They're using you to try and determine that answer. This after they've met their security criteria by using a real CAPTCHA. That means this is just unpaid labour! Wait 'till my union rep finds out about this, there'll be trouble!!
  • Any method of anti-spam that causes the user to jump through hoops is a bad design. CAPTCHAs are no more effective than a battery of tests against content at preventing spam, period. While an unscrupulous website operator can lift the CAPTCHA and get unwitting users to submit it, they can't fool systems like, say, Spam Karma [unknowngenius.com] that test for the characteristics of spam. I've been using it for quite a while and it's been 100% accurate in telling me what is or is not spam while providing zero inconvenience to th
  • How do they know if what I type is the real text, if they don't know in advance what it says.
    And if they already know what it says, then why would they need someone else to type it for the first time.
    the extent of how academics can be o out of touch with reality.
  • Maybe they can help piece together secrets from East Germany [bbc.co.uk].
  • This class of CAPTCHA is not always going to work first time, every time. It depends upon the subjective opinion or skill of the user. In my view, the ultimate CAPTCHA has been released:

    www.hotcaptcha.com [hotcaptcha.com]

"Don't worry about people stealing your ideas. If your ideas are any good, you'll have to ram them down people's throats." -- Howard Aiken

Working...