CAPTCHA stands for Completely Automated Public Turing Test to Tell Computers and Humans Apart. It really explains everything from its meaning itself. They're also known as a type of Human Interaction Proof (HIP). For humans, it appears to be very simple but not on computers. Computer will deal to all hardships to resolve captcha and if you are a computer-operated robot, solving captcha can be one of the most impossible thing to do.
And why they do this? There are some people out there who try to exploit weaknesses in the computers running the site. There are only few number of the people on the Internet but their actions can affect millions of users and Web sites. As part of security, they use CAPTCHA.
More advanced robots are now able to solve uncomplicated CAPTCHAs. If humans will only limit the capability of robots then there will no be problem. And if they are made too difficult, they will defeat even humans. Therefore, this is not a sure way to distinguish the two.
If captcha is easy, it can be solved by the robots. There are some easy pattern of captcha which can be easily solved determined. So if you will set some unique captcha which can be solved only by humans then you are safe.
This can probably prevent most bots from coming into the system. However, bots are getting more and more sophiscated so I do not think it can stop all bots from coming into the system. It definitely does help though.
CAPTCHA is a way of distinguishing humans from robots which usually come in the form of identifying various images, arithmetic problems, question-answer, riddles, simply clicking, etc. which are easily recognized, solved or answered by humans but difficult for robots. This is a preventive measure employed by companies on their websites to secure their systems are not infiltrated by suspicious hackers or attempts to steal sensitive information or any other form of cheating or security threat.
Since technology has created robots to be smarter and more human-like, there will be other creative genius who will come up with sophiscated CAPTCHAs to beat robots. Since these are products of human creations, eventually good will prevail over evil.
CAPTCHA do distinguish from bots and humans as it needs human touch to solve it; like recognizing a certain picture, reading complicated handwriting of a word, or even the special characters itself. Nowadays bots are getting smarter but so are humans, bots can now solve uncomplicated CAPTCHAs but we are also improving ourselves.
The only downside of it is that if you fail once, you will be banned from whatever your doing. Been in that situation myself.
Based on my experience, it doesn't work in some captchas because i have noticed that even i'm wrong was still it will activate even my answer was wrong, so i think recaptcha is not best way to verify a human or a robot.
Most of the time. CAPTCHA will definitely work. CAPTCHA tests are designed in a way that only human eyes and brains can solve. These tests usually are entering distorted letters and choosing correct images, which are too complicated for computers and bots to recognize. So you can say CAPTCHA does distinguish a person and a robot. Well, you can say that most of the time, because if a CAPTCHA test with the same task is repeated many times, bots can be trained in order to surpass it.
Just so you know CAPTCHAs are also used to collect data about human capabilities and feed that data into the algorithms.
Why do you think there are so many CAPTCHAs regarding streets? It's because that data is used to develop the self-driving cars.
I wonder if in a few decades CAPTCHAs get so advanced that no human will be able to solve them, only the machines.