How CAPTCHAs work | What does CAPTCHA mean? | Cloudflare
What is a CAPTCHA?
A CAPTCHA test is designed to determine if an online user is really a human and not a bot. CAPTCHA is an acronym that stands for “Completely Automated Public Turing test to tell Computers and Humans Apart. ” Users often encounter CAPTCHA and reCAPTCHA tests on the Internet. Such tests are one way of managing bot activity, although the approach has its drawbacks.
Although CAPTCHAs are designed to block automated bots, CAPTCHAs are themselves automated. They’re programmed to pop up in certain places on a website, and they automatically pass or fail users.
How does a CAPTCHA work?
Classic CAPTCHAs, which are still in use on some web properties today, involve asking users to identify letters. The letters are distorted so that bots are not likely to be able to identify them. To pass the test, users have to interpret the distorted text, type the correct letters into a form field, and submit the form. If the letters don’t match, users are prompted to try again. Such tests are common in login forms, account signup forms, online polls, and e-commerce checkout pages.
The idea is that a computer program such as a bot will be unable to interpret the distorted letters, while a human being, who is used to seeing and interpreting letters in all kinds of contexts – different fonts, different handwritings, etc. – will usually be able to identify them.
The best that many bots will be able to do is input some random letters, making it statistically unlikely that they will pass the test. Thus, bots fail the test and are blocked from interacting with the website or application, while humans are able to continue using it like normal.
Advanced bots are able to use machine learning to identify these distorted letters, so these kinds of CAPTCHA tests are being replaced with more complex tests. Google reCAPTCHA has developed a number of other tests to sort out human users from bots.
What is reCAPTCHA?
reCAPTCHA is a free service Google offers as a replacement for traditional CAPTCHAs. reCAPTCHA technology was developed by researchers at Carnegie Mellon University, then acquired by Google in 2009.
reCAPTCHA is more advanced than the typical CAPTCHA tests. Like CAPTCHA, some reCAPTCHAs require users to enter images of text that computers have trouble deciphering. Unlike regular CAPTCHAs, reCAPTCHA sources the text from real-world images: pictures of street addresses, text from printed books, text from old newspapers, and so on.
Over time, Google has expanded the functionality of reCAPTCHA tests so that they no longer have to rely on the old style of identifying blurry or distorted text. Other types of reCAPTCHA tests include:
Image recognition
Checkbox
General user behavior assessment (no user interaction at all)
How does an image recognition reCAPTCHA test work?
For an image recognition reCAPTCHA test, typically users are presented with 9 or 16 square images. The images may all be from the same large image, or they may each be different. A user has to identify the images that contain certain objects, such as animals, trees, or street signs. If their response matches the responses from most other users who have submitted the same test, the answer is considered “correct” and the user passes the test.
Picking out certain objects from blurry photos is a hard problem for computers to solve. Even advanced artificial intelligence (AI) programs struggle with it – so a bot will struggle with it as well. However, a human user should be able to do this fairly easily, since humans are used to perceiving everyday objects in all kinds of contexts and situations.
How do reCAPTCHA tests with a single checkbox work?
Some reCAPTCHA tests simply prompt the user to check a box next to the statement, “I’m not a robot. ” However, the test is not the actual action of clicking the checkbox – it’s everything leading up to the checkbox click.
This reCAPTCHA test takes into account the movement of the user’s cursor as it approaches the checkbox. Even the most direct motion by a human has some amount of randomness on the microscopic level: tiny unconscious movements that bots can’t easily mimic. If the cursor’s movement contains some of this unpredictability, then the test decides that the user is probably legitimate. The reCAPTCHA also may assess the cookies stored by the browser on a user device and the device’s history in order to tell if the user is likely to be a bot.
If the test is still unable to determine whether or not the user is a human, it may present an additional challenge, such as the image recognition test described above. However, most of the time the user’s cursor movements, cookies, and device history are conclusive enough.
How does reCAPTCHA work without any user interaction?
The latest versions of reCAPTCHA are able to take a holistic look at a user’s behavior and history of interacting with content on the Internet. Most of the time, the program can decide based on those factors whether or not the user is a bot, without providing the user with a challenge to complete. If not, then the user will get a typical reCAPTCHA challenge.
What triggers a CAPTCHA test?
Some web properties just automatically have CAPTCHAs in place as a proactive defense against bots. Other times, a test may be triggered if user behavior seems to resemble a bot’s behavior: if users request webpages or click hyperlinks at a far higher rate than average, for instance.
Are CAPTCHAs and reCAPTCHAs enough for stopping malicious bots?
Some bots can get past the text CAPTCHAs on their own. Researchers have demonstrated ways to write a program that beats the image recognition CAPTCHAs as well. In addition, attackers can use click farms to beat the tests: thousands of low-paid workers solving CAPTCHAs on behalf of bots.
Besides a CAPTCHA, there need to be other strategies in place for stopping unwanted bots (such as content scraping bots, credential stuffing bots, or spam bots).
What are the drawbacks of using CAPTCHAs or reCAPTCHAs to stop bots?
Bad user experience: A CAPTCHA test can interrupt the flow of what users are trying to do, giving them a negative view of their experience on the web property, and leading to them abandoning the webpage altogether in some cases.
Not usable for visually impaired individuals: The problem with CAPTCHAs is that they rely on visual perception. This makes them nearly impossible, not just for people who are legally blind, but for anyone with seriously impaired vision.
These tests can be fooled by bots: As described above, CAPTCHAs are not fully bot-proof and shouldn’t be relied upon for bot management.
Are there alternatives to using CAPTCHAs or reCAPTCHAs?
Bot management solutions such as Cloudflare Bot Management or Super Bot Fight Mode can identify bad bots without impacting the user experience, based on the behavior of the bot. This way, bots can be mitigated without forcing users to complete CAPTCHAs.
How are CAPTCHA and reCAPTCHA related to artificial intelligence (AI) projects?
As millions of users identify hard-to-read text and pick out objects in blurry images, that data is fed into AI computer programs so that they become better at those tasks as well.
In general, computer programs struggle with identifying objects and letters in different contexts, because context can change almost infinitely in the real world. For instance, a stop sign is a red octagon with white letters reading “STOP. ” A computer program could identify a shape-and-word combination like that fairly easily. However, a stop sign in a photo may look very different from that simple description depending on context: the angle of the photo, the lighting, the weather involved, and so on.
Via machine learning, AI programs can get better at overcoming these limitations. For the stop sign example, the programmer would feed the AI program a bunch of data on what is and is not a stop sign. For this to be effective, they need lots of examples of images with stop signs and images without stop signs, and they need human users to identify them until the program has enough data to be effective at it.
reCAPTCHA helps fill this need by getting humans to identify objects and texts, which slowly provides enough data to build robust AI programs.
What is a Turing test? How are Turing tests relevant to CAPTCHA tests?
A Turing test assesses a computer’s ability to mimic human behavior. Alan Turing, an early computing pioneer, invented the concept of a Turing test in 1950. A computer program “passes” the Turing test if its performance during the test is indistinguishable from that of a human – if it acts the way that a human would act. A Turing test is not dependent on getting answers correct; it’s about how “human” the answers sound, regardless of whether they’re right or wrong.
Although it’s called a “Public Turing test, ” a CAPTCHA is really the opposite of a Turing test – it determines whether a supposedly human user is actually a computer program (a bot) or not, instead of trying to determine if a computer is human. To accomplish this, a CAPTCHA needs to assign a brief task that people tend to be good at and computers struggle with. Identifying text and images usually fits those criteria.
Why Are Bots Unable to Check “I Am Not a Robot” Checkboxes?
Oliver Emberton:
How complicated can one little checkbox be? You can’t even imagine!
For starters, Google invented an entire virtual machine—essentially a simulated computer inside a computer—just to run that checkbox.
That virtual machine uses Google’s own language, which they then encrypt. Twice.
But this is no simple encryption. Normally, when you password protect something, you might use a key to decode it. Google’s invented language is decoded with a key that is changed by the process of reading the language, and the language also changes as it is read.
Google combines (or hashes) that key with the web address you’re visiting, so you can’t use a CAPTCHA from one website to bypass another. It further combines that with “fingerprints” from your browser, catching microscopic variations in your computer that a bot would struggle to replicate (such as CSS rules).
All of this is done just to make it hard for you to understand what Google is even doing. You need to write tools just to analyze it. (Fortunately people did just that).
It turns out that these checkboxes record and analyze a lot of data, including: Your computer’s timezone and time; your IP address and rough location; your screen size and resolution; the browser you’re using; the plugins you’re using; how long the page took to display; how many key presses, mouse clicks, and tap/scrolls were made; and… some other stuff we don’t quite understand.
We also know that these boxes ask your browser to draw an invisible image [PDF] and send it to Google for verification. The image contains things like a nonsense font, which (depending on your computer) will fall back to a system font and be drawn very differently. They then add to this a 3D image with a special texture, which is drawn in such a way that the result varies between computers.
Finally, these seemingly simple little checkboxes combine all of this data with their knowledge of the person using the computer. Almost everyone on the Internet uses something owned by Google—search, mail, ads, maps—and as you know, Google Tracks All Of Your Things™️. When you click that checkbox, Google reviews your browser history to see if it looks convincingly human.
This is easy for them, because they’re constantly observing the behavior of billions of real people.
How exactly they check all this information is impossible to know, but they’re almost certainly using machine learning (or AI) on their private servers, which is impossible for an outsider to replicate. I wouldn’t be surprised if they also built an adversarial AI to try to beat their own AI, and have both learn from each other.
So why is all this hard for a bot to beat? Because now you’ve got a ridiculous amount of messy human behaviors to simulate, and they’re almost unknowable, and they keep changing, and you can’t tell when. Your bot might have to sign up for a Google service and use it convincingly on a single computer, which should look different from the computers of other bots, in ways you don’t understand. It might need convincing delays and stumbles between key presses, scrolling and mouse movements. This is all incredibly difficult to crack and teach a computer, and complexity comes at a financial cost for the spammer. They might break it for a while, but if it costs them (say) $1 per successful attempt, it’s usually not worth them bothering.
Still, people do break Google’s protection [PDF]. CAPTCHAs are an ongoing arms race that neither side will ever win. The AI technology that makes Google’s approach so hard to fool is the same technology that is adapted to fool it.
Just wait until that AI is convincing enough to fool you.
Sweet dreams, human.
This post originally appeared on Quora. Click here to view.
Subscribe to our Newsletter!
SIGN UP NOW
By Typing Captcha, you are Actually Helping AI’s Training – AP News
Press release content from Accesswire. The AP news staff was not involved in its YORK, NY / ACCESSWIRE / November 27, 2020 / Living in the Internet age, how occasionally have you come across the tricky CAPTCHA tests while entering a password or filling a form to prove that you’re fully human? For example, typing the letters.. YORK, NY / ACCESSWIRE / November 27, 2020 / Living in the Internet age, how occasionally have you come across the tricky CAPTCHA tests while entering a password or filling a form to prove that you’re fully human? For example, typing the letters.. YORK, NY / ACCESSWIRE / November 27, 2020 / Living in the Internet age, how occasionally have you come across the tricky CAPTCHA tests while entering a password or filling a form to prove that you’re fully human? For example, typing the letters and numbers of a warped image, rotating objects to certain angles or moving puzzle pieces into is CAPTCHA and how does it work? CAPTCHA is also known as Completely Automated Public Turing Test to filter out the overwhelming armies of spambots. Researchers at Carnegie Mellon University developed CAPTCHA in the early 2000s. Initially, the program displayed some garbled, warped, or distorted text that a computer could not read, but a human can. Users were requested to type the text in a box, and have access to the program has achieved wild success. CAPTCHA has grown into a ubiquitous part of the internet user experience. Websites need CAPTCHAs to prevent the “bots” of spammers and other computer underworld types. “Anybody can write a program to sign up for millions of accounts, and the idea was to prevent that, ” said Luis von Ahn, a pioneer of early CAPTCHA team and founder of Google’s reCAPTCHA, one of the biggest CAPTCHA services. The little puzzles work because computers are not as good as humans at reading distorted text. Google says that people are solving 200 million CAPTCHAs a the past years, Google’s reCAPTCHA button saying “I’m not a robot” was followed more complicated scenarios, such as selecting all the traffic lights, crosswalks, and buses in an image grid. Soon the images have turned increasingly obscured to stay ahead of improving optical character recognition programs in the arms race with bot makers and PTCHA’s potential influence on AIWhile used mostly for security reasons, CAPTCHAs also serve as a benchmark task for artificial intelligence technologies. According to CAPTCHA: using hard AI problems for security by Ahn, Blum and Langford, “any program that has high success over a captcha can be used to solve a hard, unsolved Artificial Intelligence (AI) problem. CAPTCHAs have many applications. ”From 2011, reCAPTCHA has digitized the entire Google Books archive and 13million articles from New York Times catalog, dating back to 1851. After finishing the task, it started to select snippets of photos from Google Street View in 2012. It made users recognize door numbers, other signs and symbols. From 2014, the system started training its Artificial Intelligence (AI) warped characters users identify and fill in for reCaptcha are for a bigger purpose, as they have unknowingly transcribed texts for Google. It shows the same content to several users across the world and automatically verifies if a word has been transcribed correctly by comparing the results. Clicks on the blurry images can also help identify objects that computing systems fail to manage, and in this process Internet users are actually sorting and clarifying images to train Google’s AI rough such mechanisms, Google has been able to help users back in recognizing images, giving better Google search results, and Google Maps teBridge: an automated data annotation platform to empower AI
Turing Award winner Yann LeCun once expressed that developers need labeled data to train AI models and more quality-labeled data brings more accurate AI systems from the perspective of business and the face of AI blue ocean, a large number of data providers have poured in. has made a breakthrough with its automated data labeling platform in order to empower data scientists and AI companies in an effective a completely automated data service system, has developed a mature and transparent workflow. In ByteBridge’s dashboard, developers can create the project by themselves, check the ongoing process simultaneously on a pay-per-task model with clear estimated time and price.
thinks highly of application scenarios, such as autonomous driving, retail, agriculture and smart households. It is dedicated to providing the best data solutions for AI development and unleashing the real power of data. “We focus on addressing practical issues in different application scenarios for AI development through one-stop, automated data services. Data labeling industry should take technology-driven tool as core competitiveness, ” said Brian Cheong, CEO and founder a rare and precious social resource, data needs to be collected, cleaned and labeled before it grows into valuable goods. has realized the magic power of data and aimed at providing the best data labeling service to accelerate the development of NTACT:contact:website: company: ByteBridgephone: 010 – 53673971SOURCE: TTC Foundation View source version on
Frequently Asked Questions about robot solves captcha
Can robots solve CAPTCHA?
Some bots can get past the text CAPTCHAs on their own. Researchers have demonstrated ways to write a program that beats the image recognition CAPTCHAs as well. In addition, attackers can use click farms to beat the tests: thousands of low-paid workers solving CAPTCHAs on behalf of bots.
Why can robots not pass CAPTCHA?
Google combines (or hashes) that key with the web address you’re visiting, so you can’t use a CAPTCHA from one website to bypass another. It further combines that with “fingerprints” from your browser, catching microscopic variations in your computer that a bot would struggle to replicate (such as CSS rules).
Can an AI beat CAPTCHA?
According to CAPTCHA: using hard AI problems for security by Ahn, Blum and Langford, “any program that has high success over a captcha can be used to solve a hard, unsolved Artificial Intelligence (AI) problem. CAPTCHAs have many applications.”Nov 27, 2020