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What’s the purpose of CAPTCHA technology and how does it …
Learn about the purpose of CAPTCHA challenges that enable websites to differentiate bots from authentic users to stop spammers from hijacking forums and blog comment sections.
What is the technology used on blogs and some web search tools when a user is presented a box with letters and…
has to retype the displayed information to verify their identity or that they are the intended recipient?
This technology is CAPTCHA, an acronym for Completely Automated Public Turing test to tell Computers and Humans Apart. A CAPTCHA is usually a graphic image with a series of distorted letters on an equally distorted or multicolored background. Other types of CAPTCHA challenges require a user to identify photos, do simple arithmetic problems, provide a response to an audio snippet or simply click a box that says, “I’m not a robot. ”
The CAPTCHA algorithm is public, as the “P” in the name implies. The test was developed in various forms around 1996, but it got its distinctive name in 2000 from researchers at Carnegie Mellon University and IBM. Cracking the algorithm won’t make the CAPTCHA vulnerable, since the algorithm is only used for generating the random series of letters and numbers in the image. The system works because humans and computers process strings of characters differently.
Why is CAPTCHA important?
One of the most important reasons for CAPTCHA is to defend against ad spammers who promote their scams in comments on webpages. By requiring all users to negotiate the CAPTCHA authentication, administrators can filter out spammers who attempt to automate their activities.
CAPTCHA technology authenticates that a real person is accessing the web content to block spammers and bots that try to automatically harvest email addresses or try to automatically sign up for access to websites, blogs or forums. CAPTCHA blocks automated systems, which can’t read the distorted letters in the graphic.
How CAPTCHA works
CAPTCHA is a form of challenge-response authentication, using challenges that can easily be responded to by people but that are difficult for bots. Rather than authenticating the identity of the person accessing the resource, CAPTCHA is used to authenticate that the entity attempting to access the resource is actually human and not a bot or other piece of malicious software.
CAPTCHA challenges slow down bots trying to post spam.
CAPTCHA challenges need to be difficult enough to defeat attacks that use AI to try to solve them but easy enough for people to solve.
One of the problems with CAPTCHA is that, sometimes, the characters are so distorted that they can’t even be recognized by people with good vision — let alone visually impaired individuals. Depending on local accessibility regulations for websites, this can also be a compliance issue for some web-based businesses.
The reCAPTCHA project improves on CAPTCHA’s antibot strategy.
Even as the CAPTCHA developers continue to improve the utility, attackers are also always on the alert for new vulnerabilities and tactics for defeating CAPTCHA. In 2015, CAPTCHA-bypassing malware was discovered in Android apps offered through Google Play Store. And, early in 2019, security researchers reported the ability to bypass spoken phrases with the UnCAPTCHA proof-of-concept attack. The reCAPTCHA project aims to strengthen CAPTCHA, even as attackers continue to target it through exploits like ReBreakCAPTCHA.
When to use CAPTCHA
Use CAPTCHA for webpages that accept input from unauthenticated users. CAPTCHA is not usually needed for accepting input from users who have already logged into their accounts, but it can help slow down unauthenticated users — like bots — that try to post spammy comments in forums or blogs without the need to be authenticated as legitimate PTCHA technology is easy to implement but requires some knowledge of PHP or other web scripting languages. For more information about integrating CAPTCHA protections, check the reCAPTCHA project’s developer’s guide.
This was last published in September 2019
Dig Deeper on Web authentication and access control
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CAPTCHA (Completely Automated Public Turing Test to Tell Computers and Humans Apart)
By: Linda Rosencrance
UnCAPTCHA attack updated to bypass spoken phrases
By: Michael Heller
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6 reasons why your website needs a captcha form [updated …
[Updated for 2021]It’s thought that as many as 200 million captcha tests are completed online every day. If you’ve not got a captcha test on your own website, here’s everything you need to know about them and how they can benefit your business or blog. What is a captcha form? The word captcha is actually an acronym that stands for ‘completely automated public Turing test to tell computers and humans apart’. Quite a mouthful isn’t it? What this means, in a nutshell, is that a captcha test is a tool that helps to distinguish a human user from a computer user ptcha tests are often added to websites to stop them from receiving spam through the likes of contact forms. What do captcha forms look like? The original form of captcha tests, invented in the late 1990s, took the form of a panel of obscured letters or numbers. The letters were obscured by blurring, stretching or warping. It would then be the internet user’s task to identify these letters and type them into a separate area of the form. If they interpreted the letters correctly, they passed the test. Since the nineties, other forms of captcha tests have emerged. Sometimes, users will be shown an image with a grid over the top. They’ll then be asked to identify all areas of that grid that contain a certain feature – such as a street sign or a part of a parked car.
Users can also be asked to pick out specific words from a piece of text. This text is usually presented as a scanned page from a book or other publication. Some captchas are presented as simple sums, such as 4+1, as well. Plus, audio captchas exist for people with vision impairments. Most recently, Google started offering a captcha service called reCAPTCHA. The tech behind this test is a little bit more inquisitive than the that behind the original captchas. reCAPTCHA recognises that people can sometimes feel like they’re wasting their time filling in a captcha form. So, when a user arrives at a web page reCAPTCHA analyses the behaviour of that user to see how human-like it is. If the reCAPTCHA service deems the behaviour to be pretty life-like, it won’t serve up a complete captcha test. It will only ask the user to tick a box to confirm ‘I am not a robot’. If there’s anything robotic about the way the user interacts with a page, however, they’ll be asked to solve a more complicated captcha test. How do captcha tests work? At present, computer programmes lack the sophistication that humans have when it comes to processing visual data. Human minds are hard-wired to pick up on patterns in everything they see. People often see patterns where they are none – such as a face in the moon or the outline of Elvis on a burnt bit of toast. This phenomenon is called pareidolia. Computers, meanwhile, can be programmed to recognise letters and numbers. However, they stop recognising them when they are obscured or distorted too much. What are the benefits of a captcha form? Essentially captchas deter hackers from abusing online services because they block robot software from submitting fake or nefarious online requests. Captcha tests can be used to…Protect the integrity of online polls by stopping hackers using robots to send in repeated false brute force attacks on online accounts in which hackers repeatedly try to log-in using hundreds of different passwords. Prevent hackers from signing up for multiple email accounts that they’ll then go on to use for nefarious cyber criminals spamming blogs or news content pages with dodgy comments and links to other event ticket touts from using robots to bulk buy tickets for shows and make online shopping more secure. How have organisations suffered as a result of not having a captcha form? There are a few case studies of organisations and businesses who have suffered as a result of not having captcha forms on their websites.
One of the earliest cases dates back to the late nineties when social news website Slashdot published a poll asking visitors to vote for the best computer science graduate course in the USA. Students from two universities – Carnegie Mellon and MIT – used automated programs to vote repeatedly for their respective schools, and the poll became skewed and damagingly, in 2013 big supermarket brand Target suffered from a data breach that affected 70 million people. Commenting on the breach, Rocket Digital reported: “When Target hired a security company to investigate, one of the leading theories was that the breach was caused by malicious email – specifically a phishing email that went after their customer base. “They had a vendor portal that did not have a captcha or any kind of human verification in place, so a bot was able to get into the system and start transmitting data back to people who weren’t supposed to have iticisms of captcha forms [new content]A number of criticisms have been levelled at captcha forms over the years. The first criticism is that captcha forms detract from the user experience on a website. They’ve been called annoying and, in some cases, users may decide they are so frustrating that they’d rather leave the site they’re on entirely, rather than complete the captcha. The second big criticism of captcha forms is that they’re not very accessible. The lion’s share of captcha forms require the user to be able to see. Audio alternatives to captchas are available but one study by the National Federation for the Blind found that blind people were only able to complete these audio captchas 46 per cent of the time. More recently, Google’s reCAPTCHA technology has been attacked for consuming too much data. In April 2020 big security brand Cloudflare announced that it would be moving from using Google’s reCAPTCHA to using hCaptcha saying: “hCaptcha don’t sell personal data; they collect only minimum necessary personal data and they are transparent in describing the info they collect and how they use and/or disclose it. ” On top of this, cyber criminals are starting to use captcha forms themselves. Digital technology magazine Ars Technica recently reported: “Microsoft recently spotted an attack group distributing a malicious Excel document on a site requiring users to complete a CAPTCHA, most likely in an attempt to thwart automated detection by good guys. ” How do I add a captcha form to my website? If your website is based on WordPress, you can add a captcha plugin to your site. There are lots of options in the WordPress plugin directory, but you’ll want to choose one that has been updated recently and has a decent amount of active installations – like reCaptcha by BestWebSoft. For other websites, you might need a little bit of tech experience, in the form of HTML knowledge, to add a captcha to your website. If your business has its own web development team then they can do it easily and quickly in-house, or you can contact your web designer to complete the task for you. Google offers developers detailed instructions on how to install a reCAPTCHA, for free, on its help pages. hCaptcha also features a developer guide on its future of captcha? [new content]As bots become more sophisticated, captchas will need to keep up. Industry commentators suggest that an element of gamification may need to be added to captchas of the future – although this doesn’t solve the accessibility issue. Other experts suggest that captchas may eventually be replaced altogether with biometric checks – such as quick eye scans. Need more protection for your website? Check out our Sucuri website security product. With prices starting at just £4. 99 a month, it polices websites for malware and purges any it detects. Find out more on our Security Pages.
Why do we need CAPTCHAs? | Onsight
There is no doubt that if you’re a regular user of the Internet that you have seen what is called a CAPTCHA box, usually when you are leaving a comment, creating an account or logging in somewhere. What are these mysterious puzzles and why are they so necessary to decode when trawling the Internet?
What is a CAPTCHA?
CAPTCHA is an acronym that stands for “Completely Automated Public Turing test to tell Computers and Humans Apart”. Quite a mouthful. It was coined in 2000 by professors and scientists from Carnegie Mellon University and IBM.
A CAPTCHA is what is called a challenge-response test. One party presents a question or challenge and the other party must provide a valid answer or response in order to be authenticated.
The CAPTCHA idea originally comes from the Turing test (as can be seen in the above acronym). A Turing test is a means with which to test a machine’s ability to exhibit intelligent behaviour equivalent to that of a human being. A CAPTCHA can be called a reverse Turing test since it is a computer creating the test in the first place that will challenge humans and not the other way around.
Which purposes does CAPTCHA serve?
CAPTCHA prevents spam in website comment sections and on blogs. Many spammers bombard comment sections with links to increase search engine rankings. The test makes sure only humans comment and users don’t have to sign in beforehand to leave a comment.
Many companies offer free email services but a while ago bots would sign up for hundreds of free accounts and then use these accounts to cause havoc on the Internet. Now people need to complete a CAPTCHA before being able to get a free email account. Free services should be protected by CAPTCHA to prevent abuse via automated scripts.
It offers protection from scrapers who want to copy the email addresses of users. Spammers would crawl the Internet for email addresses that are posted in clear text. By utilising CAPTCHA you can protect against these scrapers. People need to solve a CAPTCHA before an email address is shown.
Sometimes people don’t want a webpage to be shown so there is an HTML tag that hides the page from robots. Big search engine companies respect this but sometimes it doesn’t prevent all bots from coming through. This is what CAPTCHA helps to prevent.
Often people will use programs to stuff online polls in favour of a certain vote. Usually IP addresses are recorded to prevent people from voting more than once but with the use of bots one can circumvent this policy. This makes it hard to truly trust online polls if CAPTCHA codes are not involved.
Dictionary attacks are when a computer goes through every word in a dictionary in order to obtain access to someone’s password and account. CAPTCHAs prevents this by requiring the computer (or person) to enter a code after a certain amount of unsuccessful logins.
The prevention of torrent sites from bots falsifying seed counts and positive reviews in order to trick people into download a Trojan virus.
Issues with CAPTCHA technology
CAPTCHAs are sometimes only based on reading texts – which is a problem for people who are visually impaired and subsequently not everyone can access a protected resource, no matter if they truly are human. The most effective way around it is to allow a person to opt for an audio or sound-based CAPTCHA.
Some CAPTCHA images are not properly distorted. It may be using text that is completely undistorted or have only minor distortions. This will not deter bots from accessing protected resources because it is like reading normal text, something a bot can easily do.
Secure CAPTCHA code is not easy to build and there needs to be made sure that the CAPTCHA cannot be worked around at script level. Some script issues that can occur include systems passing the answer to the CAPTCHA in plain text and systems where the same answer can be used to solve multiple CAPTCHAs.
If too many sites start using a certain type of CAPTCHA, it can cause the system to become insecure and no longer valid. Puzzles that usually ask text-based questions is an example of this and they seem to be easy to circumvent if you can program a bot to learn the answer.
So next time you are confronted with a CAPTCHA and you’re scratching your head, remember that they are confusing bits of text for very good reasons – to protect your information and defeat bots!