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Topic: Captcha

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	CAPTCHAs :: Software Development :: Vancouver - Toronto, Canada (Site not responding. Last check: 2007-10-12)
		A captcha (an acronym for "completely automated public Turing test to tell computers and humans apart") is a type of challenge-response test used in computing to determine whether or not the user is human.
		Captchas are used to prevent bots from using various types of computing services.
		Audio captchas appear to be the dominant working solution to this problem (intensified in the USA by the "Americans with Disabilities Act").
	www.softwaredevelopment.ca /captchas.shtml (386 words)

	captcha [Wiki:NucleusCMS]
		Captcha challenges can be solved by most people, but most bots are currently unable to do so.
		To test the captchas after installing the plugin, you’ll need to either log out or use another browser from which you’re not logged in.
		To verify that captcha images are being generated and to find the problem when they aren’t, log out and visit your site as an anonymous user.
	wakka.xiffy.nl /captcha (901 words)

	CAPTCHA - a Whatis.com definition
		A CAPTCHA (Completely Automated Public Turing Test to tell Computers and Humans Apart) is a challenge-response system test designed to differentiate humans from automated programs.
		A CAPTCHA differentiates between human and bot by setting some task that is easy for most humans to perform but is more difficult and time-consuming for current bots to complete.
		CAPTCHAs are often used to stop bots and other automated programs from using blogs (see splog) to affect search engine rankings, signing up for e-mail accounts to send out spam or take part in on-line polls.
	whatis.techtarget.com /gDefinition/0,294236,sid11_gci950098,00.html (386 words)

	ONLamp.com -- Securing Web Forms with PEAR's Text_CAPTCHA
		CAPTCHA, or "completely automated public Turing test to tell computers and humans apart," is a project of the Carnegie Mellon School of Computer Science that sets out to determine if a human or a computer initiated a request.
		CAPTCHA technology enables you to discern human requests from computer generated requests on the Web, where such a distinction is difficult.
		Remember, CAPTCHA is a technology for telling humans apart from computers, not just for generating images to do so.
	www.onlamp.com /pub/a/php/2005/03/31/text_captcha.html (1449 words)

	Authen::Captcha - Perl extension for creating captcha's to verify the human element in transactions.
		It can also be called in array context to retrieve the string of characters used to generate the captcha (the string the user is expected to respond with).
		These are used in the generation of the final captcha image file.
		This means that the created captcha's will not remain valid forever, just as long as you want them to be active.
	cpan.uwinnipeg.ca /htdocs/Authen-Captcha/Authen/Captcha.html (892 words)

	Proposal for an Accessible Captcha- Standards Schmandards (via CobWeb/3.1 planetlab-2.cs.princeton.edu) (Site not responding. Last check: 2007-10-12)
		Captchas are often used to prevent automated mass registration of accounts to online services such as web mail, site forums and auction sites.
		Generating test instances with my captcha audio generator also creates a table linking audio files to the numbers the user is supposed to enter.
		Captchas are a nice alternative for public ‘collaboration’, especially when you want real feedback without turning users away by requiring logins (and lots of annoying info like address, phone, etc).
	www.standards-schmandards.com.cob-web.org:8888 /index.php?2005/01/01/11-captcha (3522 words)

	Home
		CAPTCHAs are designed to prevent bots – programs that pose as humans on the Internet – from abusing internet services.
		For example, users registering on Yahoo must first correctly recognize a distorted word displayed against a cluttered background and type it into a box to prove they are human.
		Such reading-based CAPTCHAs exploit the large gap between humans and machines in their ability to read images of text.
	www2.parc.com /istl/projects/captcha (269 words)

	CAPTCHA Codes are not Accessible
		CAPTCHA tests are showing up like crazy these days to validate that users are humans, and not computers.
		I think that most people implementing captcha's these days are overlooking the fact that they are not accessible, and they would fail Section 508 accessibility compliance for a web application.
		Some CAPTCHA codes are hard for me to read and I am not color blind, and have 20/20 vision.
	www.petefreitag.com /item/376.cfm (614 words)

	CAPTCHA if they can
		CAPTCHA works by presenting an image of a word that has been distorted and obscured so that a computer is not able to recognise it, while a human still can.
		For example, the text of the word "plus" on the right was skewed and placed on a patterned background, before the image was chopped up into a number of pieces.
		Yahoo are now preventing this by putting a CAPTCHA style question in their standard registration forms.
	plus.maths.org /issue23/news/captcha (408 words)

	Ravis 2004 :: Captcha
		A captcha is a way to determine human users from computers, and usually involves in image that is hard for computers to decode, but easy for humans to do so.
		I threw together a quick Captcha script in PHP for an upcoming project, and wasn't able to find any that would be sufficiently discouraging for someone to write a script to circumvent.
		I'm working on a fourth captcha based on Static (which I started building as a proof of concept) that should be by far the most secure yet, and addresses all the weaknesses mentioned above.
	www.ravis.org /code/captcha (668 words)

	Alagad Captcha (Site not responding. Last check: 2007-10-12)
		Captcha is an acronym for "completely automated public Turing test to tell computers and humans apart".
		Captcha images tend to be used on web forms to prevent automated submission by computers.
		Because the Alagad Captcha is written in pure ColdFusion and instantiates only native Java objects, it compiles with the rest of your CFML files to Java bytecode.
	www.alagad.com /index.cfm/name-captcha (208 words)

	Inaccessibility of CAPTCHA
		Larger sites adopted CAPTCHA because their resources were easy to abuse for the purposes of sending spam or conducting anonymous, illegal activity.
		CAPTCHA is now in frequent use in the comment areas of message boards and personal weblogs.
		Another heuristic approach identified in [KILLBOTS] involves the use of CAPTCHA images, with a twist: how the user reacts to the test is as important as whether or not it was solved.
	www.w3.org /TR/turingtest (3453 words)

	[No title]
		A solution was needed, and it came in the form of a simple test known as CAPTCHA (ostensibly standing for Completely Automated Public Turing Test to tell Computers and Humans Apart, according to Carnegie Mellon University, but some consider it merely shorthand for "Capture Characters").
		Captcha tests present the user with a customized graphic consisting of a series of letters and numbers that have been mangled in some way.
		Unfortunately, captchas were not perfect, and bots that made use of increasingly clever optical character recognition programs were able to defeat them.
	arstechnica.com /news.ars/post/20060407-6554.html (602 words)

	The CAPTCHA Project.
		Advancing AI Since CAPTCHAs are based on open problems in artificial intelligence (AI), they also offer well-defined challenges for the AI community, and induce security researchers, as well as otherwise malicious programmers, to advance the field of AI.
		CAPTCHAs are thus a win-win situation: either a CAPTCHA is not broken and there is a way to differentiate humans from computers, or the CAPTCHA is broken and an AI problem is solved.
		CAPTCHA is a trademark of Carnegie Mellon University.
	www.captcha.net (749 words)

	captchas.net (Site not responding. Last check: 2007-10-12)
		A CAPTCHA image shows a random string which the user has to type to submit a form.
		This is a simple problem for (seeing) humans, but a very hard problem for computers which have to use character recognition, especially, because the displayed string is alienated in a way, which makes it very hard for a computer to decode.
		The password is computed by the CAPTCHA server to generate the image and by your server to validate the users input.
	captchas.net (536 words)

	How to Spoof-proof Your Logins
		A captcha method presents a problem that's relatively easy for humans to solve, but difficult or impossible for computers to solve at this time.
		You can use the difference in machine/human reading capability to your advantage by presenting text that you know is difficult for OCR engines to read, giving you a modicum of assurance that the request for a new account or a login comes from a human user rather than a machine.
		In response, you can make the captchas more difficult to read by obscuring the text with even more random arcs, lines, or background patterns; however, if you overdo it deciphering the text becomes a challenge and a chore for legitimate users.
	www.devx.com /dotnet/Article/21308/1954 (2549 words)

	Access Matters » Blog Archive » Quiz 1.1.5: Did a CAPTCHA catch ya?
		Captchas somehow are a good idea on the surface, but it once again smacks of sharing your problem of spam with the visitor.
		Their primary purpose is to make it fairly easy for humans with good intentions to gain access to a system and very difficult for all but the most determined spammers, human or spammers, to crack and exploit in a way that becomes a nuisance.
		CAPTCHA is not not a true Turing test, it doesn’t really test intelligence, it merely tests perceptual skills, which quite apart from being ambiguous in just the ways we’re discussing here, is nothing to do with intelligence.
	www.access-matters.com /2005/05/22/quiz-115-did-a-captcha-catch-ya (2944 words)

	Word Spy - captcha
		The captcha is based on the fact that people can easily analyze images that flummox computers.
		In 1950, the mathematician Alan Turing suggested that a computer could earn the label "intelligent" if it could fool a person into thinking he or she was communicating with another person instead of a machine.
		A captcha is mostly interested in the opposite scenario: proving that a Web form (or whatever) is being submitted by a human instead of a computer program.
	www.wordspy.com /words/captcha.asp (534 words)

	Defending Against Comment Spam (UrbanMainframe.com)
		A CAPTCHA is a "program that can generate and grade tests that most humans can pass [and that] current computer programs can't pass." Which is exactly what is needed to protect against automated spamming tools.
		If such a problem did manifest itself, it would be easy to degrade the CAPTCHA image to the point where a human would still be able to decipher the embedded text but an OCR program, however advanced, would not.
		As each CAPTCHA is created, I store the word used, a timestamp (which will be used to "expire" sessions) and a session key in an SQL database on the server.
	urbanmainframe.com /folders/blog/20040323 (2156 words)

	Six Apart Guide to Combatting Comment Spam
		Perhaps the most famous Turing-style test in use as an anti-spam technique is the CAPTCHA (a cutesy acronym that stands for "Completely Automated Public Turing test to tell Computers and Humans Apart").
		CAPTCHAs frequently come in the form of images of fuzzy or distorted letters and numbers, which humans can read and parrot into a text field, but which automated optical character recognition software has trouble identifying.
		Plus, because CAPTCHAs are in use on numerous high-profile sites, such as Yahoo Groups and PayPal, spammers have devoted significant effort into automating ways to solve them.
	www.sixapart.com /pronet/comment_spam (6225 words)

	Introduction to "Inaccessibility of CAPTCHA"
		CAPTCHA stands for Completely Automated Public Turing Test to Tell Computers and Humans Apart.
		CAPTCHA and other security tests are designed to block software robots from interacting with a Web site.
		Most of these tests also block humans who are blind, deaf, hard of hearing, have low vision, or a cognitive/intellectual disability such as dyslexia.
	www.w3.org /WAI/intro/captcha.php (291 words)

	Decoding CAPTCHA image using PHP (Site not responding. Last check: 2007-10-12)
		Why are we using it is because the the CAPTCHA have a fixed offset, simple character font and a clear background.
		If the character in the CAPTCHA image happens to be "0" and "U" is placed ahead of the number "0" for comparison, there is a chance that the value decoded would be "U" instead of "0" since both should have almost identical pixel index.
		In another words, all the x, y points used to return the color of index for that character must not be the color of the background in order to be the matching result), you should be able to find the correct character that matches the condition.
	captcha.megaleecher.net (851 words)

	PWNtcha - captcha decoder (via CobWeb/3.1 planetlab-2.cs.princeton.edu) (Site not responding. Last check: 2007-10-12)
		This project’s goal is to demonstrate the inefficiency of many captcha implementations.
		A weak captcha that is not always human-solvable.
		A pretty good captcha that uses a wide variety of backgrounds, fonts and deformations.
	sam.zoy.org.cob-web.org:8888 /pwntcha (676 words)

	What is CAPTCHA? - a definition from Whatis.com
		- A CAPTCHA (Completely Automated Public Turing Test to tell Computers and Humans Apart) is a challenge-response system test designed to differentiate humans from automated programs.
		In such a system, the human listens to a series of letters or short words and types what he hears to prove he is not a bot.
		A Math CAPTCHA uses numbers instead of letters and asks the human to solve a simple mathematical calculation (4 +3 =) and record the answer.
	searchsecurity.techtarget.com /sDefinition/0,,sid14_gci950098,00.html (413 words)

	Web Sites - Captcha - Don't Go Online Without It
		Remember those old American Express commercials created by Ogilvy and Mather, ‘Don’t leave home without it?’ Well the same could be said about those identity checkers you see on blogs and websites, otherwise known as captchas.
		Actually, CAPTCHA stands for “Completely Automated Public Turing test to tell Computers and Humans Apart”.
		Whether it be completing online registration forms for web-based emails so they can spam you later or targeting online contests so they can stack the odds of winning in their favour.
	www.onedegree.ca /2006/07/27/captcha-dont-go-online-without-it (365 words)

	15 Seconds : Fighting Spambots with .NET and AI
		We experience various forms of CAPTCHAs in our everyday lives, for instance, signing up for an email account, performing DNS lookup (whois), or using images to differentiate between a person and a software program.
		The CAPTCHA Project is a project of the School of Computer Science at Carnegie Mellon University.
		But reading a simple text-based CAPTCHA image with a predictable grid was much easier than a skewed, twisted, and distorted image built to baffle the bots.
	www.15seconds.com /issue/040202.htm (2698 words)

	OCR Research Team (Site not responding. Last check: 2007-10-12)
		We have improved some parameters, and released version 1.0.1, all who bought our CAPTCHA can request new version for free, as dialed :) All who thinks about buying it - it became better, and all who will buy it gets all newer versions for free on demand.
		Yes, we know that site was freezed for a long time, but now we have improved it, and seems like now we have an ability to keep it actual.
		Another primitive CAPTCHA was implemented at UMC (biggest competitor of KS).
	www.ocr-research.org.ua (382 words)

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