Purpose Of Captcha Code
What Does CAPTCHA Mean? | CAPTCHA Types & Examples
What is CAPTCHA
CAPTCHA stands for the Completely Automated Public Turing test to tell Computers and Humans Apart. CAPTCHAs are tools you can use to differentiate between real users and automated users, such as bots. CAPTCHAs provide challenges that are difficult for computers to perform but relatively easy for humans. For example, identifying stretched letters or numbers, or clicking in a specific area.
What are CAPTCHAs Used for
CAPTCHAs are used by any website that wishes to restrict usage by bots. Specific uses include:
Maintaining poll accuracy—CAPTCHAs can prevent poll skewing by ensuring that each vote is entered by a human. Although this does not limit the overall number of votes that can be made, it makes the time required for each vote longer, discouraging multiple votes.
Limiting registration for services—services can use CAPTCHAs to prevent bots from spamming registration systems to create fake accounts. Restricting account creation prevents waste of a service’s resources and reduces opportunities for fraud.
Preventing ticket inflation—ticketing systems can use CAPTCHA to limit scalpers from purchasing large numbers of tickets for resale. It can also be used to prevent false registrations to free events.
Preventing false comments—CAPTCHAs can prevent bots from spamming message boards, contact forms, or review sites. The extra step required by a CAPTCHA can also play a role in reducing online harassment through inconvenience.
How Does CAPTCHA Work
CAPTCHAs work by providing information to a user for interpretation. Traditional CAPTCHAs provided distorted or overlapping letters and numbers that a user then has to submit via a form field. The distortion of the letters made it difficult for bots to interpret the text and prevented access until the characters were verified.
This CAPTCHA type relies on a human’s ability to generalize and recognize novel patterns based on variable past experience. In contrast, bots can often only follow set patterns or input randomized characters. This limitation makes it unlikely that bots will correctly guess the right combination.
Since CAPTCHA was introduced, bots that use machine learning have been developed. These bots are better able to identify traditional CAPTCHAs with algorithms trained in pattern recognition. Due to this development, newer CAPTCHA methods are based on more complex tests. For example, reCAPTCHA requires clicking in a specific area and waiting until a timer runs out.
Drawbacks of Using CAPTCHA
The overwhelming benefit of CAPTCHA is that it is highly effective against all but the most sophisticated bad bots. However, CAPTCHA mechanisms can negatively affect the user experience on your website:
Disruptive and frustrating for users
May be difficult to understand or use for some audiences
Some CAPTCHA types do not support all browsers
Some CAPTCHA types are not accessible to users who view a website using screen readers or assistive devices
CAPTCHA Types: Examples
Modern CAPTCHAs fall into three main categories—text-based, image-based, and audio.
Text-based CAPTCHAs
Text-based CAPTCHAs are the original way in which humans were verified. These CAPTCHAs can use known words or phrases, or random combinations of digits and letters. Some text-based CAPTCHAs also include variations in capitalization.
The CAPTCHA presents these characters in a way that is alienated and requires interpretation. Alienation can involve scaling, rotation, distorting characters. It can also involve overlapping characters with graphic elements such as color, background noise, lines, arcs, or dots. This alienation provides protection against bots with insufficient text recognition algorithms but can also be difficult for humans to interpret.
Text-based CAPTCHA patterns
Techniques for creating text-based CAPTCHAs include:
Gimpy—chooses an arbitrary number of words from an 850-word dictionary and provides those words in a distorted fashion.
EZ-Gimpy—is a variation of Gimpy that uses only one word.
Gimpy-r—selects random letters, then distorts and adds background noise to characters.
Simard’s HIP—selects random letters and numbers, then distorts characters with arcs and colors.
CAPTCHA Image
Image-based CAPTCHAs were developed to replace text-based ones. These CAPTCHAs use recognizable graphical elements, such as photos of animals, shapes, or scenes. Typically, image-based CAPTCHAs require users to select images matching a theme or to identify images that don’t fit.
You can see an example of this type of CAPTCHA below. Note that it defines the theme using an image instead of text.
Example of image-based CAPTCHA
Image-based CAPTCHAs are typically easier for humans to interpret than text-based. However, these tools present distinct accessibility issues for visually impaired users. For bots, image-based CAPTCHAs are more difficult than text to interpret because these tools require both image recognition and semantic classification.
Audio CAPTCHA
Audio CAPTCHAs were developed as an alternative that grants accessibility to visually impaired users. These CAPTCHAs are often used in combination with text or image-based CAPTCHAs. Audio CAPTCHAs present an audio recording of a series of letters or numbers which a user then enters.
These CAPTCHAs rely on bots not being able to distinguish relevant characters from background noise. Like text-based CAPTCHAs, these tools can be difficult for humans to interpret as well as for bots.
Math or Word Problems
Some CAPTCHA mechanisms ask users to solve a simple mathematical problem such as “3+4” or “18-3”. The assumption is that a bot will find it difficult to identify the question and devise a response. Another variant is a word problem, asking the user to type the missing word in a sentence, or complete a sequence of several related terms. These types of problems are accessible to vision impaired users, but at the same time they may be easier for bad bots to solve.
Social Media Sign In
A popular alternative to CAPTCHA is requiring users to sign in using a social profile such as Facebook, Google or LinkedIn. The user’s details will be automatically filled in using single sign on (SSO) functionality provided by the social media website.
This is still disruptive, but may actually be easier for the user to complete than other forms of CAPTCHA. An additional benefit is that it is a convenient registration mechanism.
No CAPTCHA ReCAPTCHA
This type of CAPTCHA, known for its use by Google, is much easier for users than most other types. It provides a checkbox saying “I am not a robot” which users need to select – and that’s all. It works by tracking user movements and identifying if the click and other user activity on the page resembles human activity or a bot. If the test fails, reCAPTCHA provides a traditional image selection CAPTCHA, but in most cases the checkbox test suffices to validate the user.
Imperva Bot Detection: CAPTCHA as a Last Line of Defense
Imperva provides a bot detection solution that is built for minimal business disruption. It offers several types of challenges which filter out bad bot traffic with minimal impact on human users—including device fingerprinting, cookie challenges and JavaScript challenges.
Imperva provides the option to deploy CAPTCHAs, but uses it as the final line of defense, if all other bot identification mechanisms fail. This means it will be used for a very small percentage of user traffic. Imperva does provide the option to manually enforce CAPTCHA, for websites that need a stricter approach to advanced bot protection.
In addition to providing bad bot mitigation, Imperva provides multi-layered protection to make sure websites and applications are available, easily accessible and safe. The Imperva application security solution includes:
DDoS Protection—maintain uptime in all situations. Prevent any type of DDoS attack, of any size, from preventing access to your website and network infrastructure.
CDN—enhance website performance and reduce bandwidth costs with a CDN designed for developers. Cache static resources at the edge while accelerating APIs and dynamic websites.
Cloud WAF—permit legitimate traffic and prevent bad traffic. Safeguard your applications at the edge with an enterprise‑class cloud WAF.
Gateway WAF—keep applications and APIs inside your network safe with Imperva Gateway WAF.
RASP—keep your applications safe from within against known and zero‑day attacks. Fast and accurate protection with no signature or learning mode.
What is Captcha? – Panda Security
When entering credentials or credit card information on websites, you might be asked to copy a series of words or a math sum to continue. While most of the time this is a quick step before you can continue your activity, many people wonder what a CAPTCHA is? And what is its purpose?
What does CAPTCHA mean?
CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart. In other words, CAPTCHA determines whether the user is real or a spam robot. CAPTCHAs stretch or manipulate letters and numbers, and rely on human ability to determine which symbols they are.
How Does a CAPTCHA Work?
CAPTCHAs were invented to block spammy software from posting comments on pages or purchasing excess items at once. The most common form of CAPTCHA is an image with several distorted letters. It is also common to choose from a variety of images where you need to select a common theme.
The internet and computers are actually made up of a unique coding language. Computers find it difficult to understand languages because of the strange and intricate rules human languages take on, along with slang that humans use.
Who Uses CAPTCHA?
CAPTCHA is used on a variety of websites that want to verify that the user is not a robot. First and foremost, CAPTCHA is used for verifying online polls. In 1999, Slashdot created a poll that asked visitors to choose the graduate school that had the best program for computer science. Students from the universities Carnegie Mellon and MIT created bots, or automated programs to repeatedly vote for their schools.
These schools received thousands of votes, while other schools only hit a few hundred. CAPTCHA came into play so that users could not take advantage of the polling system.
Another use of CAPTCHA is for registration forms on websites such as Yahoo! Mail or Gmail where people can create free accounts. CAPTCHAs prevent spammers from using bots to create a plethora of spam email accounts.
Ticket websites such as TicketMaster also use CAPTCHA to prevent ticket scalpers from over purchasing tickets for large events. This allows legitimate customers to purchase tickets fairly and keeps scalpers from placing thousands of ticket orders.
Lastly, web pages or blogs that contain message boards or contact forms use CAPTCHA to prevent spammy messages or comments. It does not prevent against cyberbullying, but does prevent bots from posting messages automatically.
Do CAPTCHA’s Work?
Unfortunately, as technology and hackers become more advanced, so do their scamming tactics. While CAPTCHA is safe for the most part, cybercriminals have begun incorporating CAPTCHA into their false or fraudulent websites to make their scams more believable.
Here are some ways that cyber criminals can trick internet users:
The scam contains intriguing messages on your newsfeed. Ex. KIM KARDASHIAN NEVER BEFORE SEEN VIDEO LEAKED. Once you click on this post, you will need to enter a fake CAPTCHA code and be directed to a landing page. At this time, a virus takes over your account.
The scam contains an outlandish title ex. GIRL ACCIDENTALLY TEXTS MOM INSTEAD OF BOYFRIEND that intrigues users to read a story. The link leads to a fake news site where software hacking may begin.
How CAPTCHA Prevents Scammers
CAPTCHA has a variety of applications for keeping websites and users secure. These include but are not limited to:
Protecting email addresses from scammers
Protect website registrations
Protects online polling
Protects against email worms/junk mail
Prevents dictionary attacks
Prevents comment spamming on blogs
History of CAPTCHA
The term CAPTCHA was first used by computer scientists at Carnegie Mellon University in 2000. While the acronym makes sense (automated test to tell computers and humans apart), the Turing Test portion may be unfamiliar.
The Turing Test
Alan Turing, known as the father of modern computing, proposed this test as an experiment to see if machines could think or appear to think like humans. The Turing Test is based on imitation. An interrogator asks two participants a series of questions. One of the participants is a machine while the other is human. The interrogator does not know which one is which and attempts to guess which participant is a machine. If the interrogator fails to figure it out, the machine has passed the Turing Test.
While CAPTCHA is meant to trick machines and create a test that only humans pass, this test was created in order for the CAPTCHA application to present a variety of CAPTCHAs to different users.
Another reason why CAPTCHA is seen as difficult to read for computers is its visual component. Because the symbols are in an image format, it’s more difficult for computers to scan an image with text, especially when the text is distorted. Humans can look at an image and detect patterns more easily.
In addition to visual patterns, CAPTCHAs also come in an audible format for the visually impaired. In some cases, CAPTCHAs may ask a reader to interpret a short passage of text. It will then prompt the reader to take a short quiz of the material.
How to Keep CAPTCHA Codes Secure
If your website needs proper protection from scammers, it’s recommended to use a CAPTCHA. There are a few extra measure to take when using any CAPTCHA code:
Secure images: Images should be distorted randomly when presented to the user. With minor distortions, the image is more vulnerable to automated attacks.
Unique CAPTCHAs: If every site used similar CAPTCHA codes, hackers could catch on and create bots that would bypass this test. That’s why it’s important to change the type of CAPTCHAs every so often and avoid common mathematical equations such as 1+1.
Script Security: In addition to making sure your images are unreadable by computers, you should also ensure that there are no easy ways around the script level.
This includes:
A system passes the answer to the CAPTCHA in plain text as part of a web form.
A system where the solution to the same CAPTCHA can be used multiple times. It’s best to avoid any CAPTCHA scripts that are found freely on the web, as these are more vulnerable to attacks.
Accessibility: CAPTCHAs need to be accessible for every user. In this regard, CAPTCHAs cannot be based solely on reading text or choosing images. It’s important that users have the opportunity to opt for an audio CAPTCHA if needed.
If a website or blog owner chooses to forgo the use of CAPTCHA, they would have significant problems with spam registrants and comments on a daily basis. Many spammers or spam software look to find cracks in the system in order to hack your website. According to Microsoft research experts Kumar Chellapilla and Patrice Simard, humans have about an 80 percent success rate at solving any CAPTCHA, but machines only have a 0. 01 success rate.
Therefore, it is beneficial to use CAPTCHA in order to keep your website safe. While the idea of creating your own CAPTCHA sounds ideal, we don’t recommend creating one because of the many failure modes that you may run into. We recommend a website that creates one for you such as reCAPTCHA from Google. In order to keep your device safe in addition to CAPTCHA, be sure to download an antivirus to stay secure.
Sources:
| How Stuff Works | Digital Unite | Captcha |
Panda Security specializes in the development of endpoint security products and is part of the WatchGuard portfolio of IT security solutions. Initially focused on the development of antivirus software, the company has since expanded its line of business to advanced cyber-security services with technology for preventing cyber-crime.
What’s the purpose of CAPTCHA technology and how does it …
Laurent –
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)
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UnCAPTCHA attack updated to bypass spoken phrases
By: Michael Heller
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Frequently Asked Questions about purpose of captcha code
Why CAPTCHA code is required?
CAPTCHA is used on a variety of websites that want to verify that the user is not a robot. … Another use of CAPTCHA is for registration forms on websites such as Yahoo! Mail or Gmail where people can create free accounts. CAPTCHAs prevent spammers from using bots to create a plethora of spam email accounts.Jan 9, 2019
What is the use of CAPTCHA code?
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 does a CAPTCHA work?
The most common form of CAPTCHA is an image of several distorted letters. It’s your job to type the correct series of letters into a form. If your letters match the ones in the distorted image, you pass the test. … The CAPTCHA test helps identify which users are real human beings and which ones are computer programs.Aug 18, 2008
