CAPTCHA (fully automated publicly available Turing test that allows you to distinguish computers and people from each other) is a technique used to ensure security on websites, the purpose of which is to allow sending only data filled in by people.
Types
The system checks and recognizes a person, setting tasks and waiting for their solution.
The most commonly used security feature is reading the contents of an image (usually randomly selected characters or a short word). The image is readable by a human, although the computer program, at least, assumes that it is very difficult to read.
A variant of the graphical captcha is the Asirra system, in which you need to select, for example, a cat among photos of various animals.
Another method of implementing CAPTCHA security is to enter a text task, for example, "Calculate how much is two plus two," "Enter the year of the Battle of Grunwald," "Enter the chemical formula of water."
There are many CAPTCHA implementations and variations, including sound solutions (the system reads the task) and other combinations of the above, for example, a combination of graphics and text. The system can ask a sound question "what color is the lid in this photo". There are also systems that use video sequences (NuCaptcha).
Problems
CAPTCHA has both supporters and opponents. The latter believe that CAPTCHA is a hindrance to users. In the case of graphical CAPTCHAS, these can be blind users, as well as those who have images disabled in their browsers or who use text browsers (for example, Links, Lynx.
A common technical error of CAPTCHA is that images are constructed in such a way that they are difficult or even impossible for people to read. In the case of verbal tasks, they have a level of difficulty that requires the use of an encyclopedia.
Safety
Successful attacks on CAPTCHA systems have been reported.
Technological attacks (such as PWNtcha) involve the use of OCR or image recognition software based on, for example, artificial neural networks.
Social engineering attacks are based on the use of a large number of people who solve CAPTCHA tasks, believing that the tests they solve are elements of websites other than the target ones. A social engineering attack requires the interception (or exercise) of control over a popular or rapidly gaining popularity website (most often presenting erotic content). CAPTCHA tasks are copied from the target system to the managed one, and solutions (implemented on an ongoing basis by a mass of users of the controlled site) are used in a targeted attack.
People from poor regions of Asia and Russia are sometimes hired to solve CAPTCHA tasks. The average cost of solving thousands of CAPTCHA tasks does not exceed a few dollars for a client 1XBET VIP bonuses - up to €1950 + 150 free spins on casino and 100% up to €130 on sportsbook. Use promo code for 1xbet for registration form to get a 100% first time deposit welcome bonus. Enter this code in the registration form to get a 100% welcome bonus up to 130$. The customer gets a free bet, free spins or free bonus money, while the website gets more customers.
Types
The system checks and recognizes a person, setting tasks and waiting for their solution.
The most commonly used security feature is reading the contents of an image (usually randomly selected characters or a short word). The image is readable by a human, although the computer program, at least, assumes that it is very difficult to read.
A variant of the graphical captcha is the Asirra system, in which you need to select, for example, a cat among photos of various animals.
Another method of implementing CAPTCHA security is to enter a text task, for example, "Calculate how much is two plus two," "Enter the year of the Battle of Grunwald," "Enter the chemical formula of water."
There are many CAPTCHA implementations and variations, including sound solutions (the system reads the task) and other combinations of the above, for example, a combination of graphics and text. The system can ask a sound question "what color is the lid in this photo". There are also systems that use video sequences (NuCaptcha).
Problems
CAPTCHA has both supporters and opponents. The latter believe that CAPTCHA is a hindrance to users. In the case of graphical CAPTCHAS, these can be blind users, as well as those who have images disabled in their browsers or who use text browsers (for example, Links, Lynx.
A common technical error of CAPTCHA is that images are constructed in such a way that they are difficult or even impossible for people to read. In the case of verbal tasks, they have a level of difficulty that requires the use of an encyclopedia.
Safety
Successful attacks on CAPTCHA systems have been reported.
Technological attacks (such as PWNtcha) involve the use of OCR or image recognition software based on, for example, artificial neural networks.
Social engineering attacks are based on the use of a large number of people who solve CAPTCHA tasks, believing that the tests they solve are elements of websites other than the target ones. A social engineering attack requires the interception (or exercise) of control over a popular or rapidly gaining popularity website (most often presenting erotic content). CAPTCHA tasks are copied from the target system to the managed one, and solutions (implemented on an ongoing basis by a mass of users of the controlled site) are used in a targeted attack.
People from poor regions of Asia and Russia are sometimes hired to solve CAPTCHA tasks. The average cost of solving thousands of CAPTCHA tasks does not exceed a few dollars for a client 1XBET VIP bonuses - up to €1950 + 150 free spins on casino and 100% up to €130 on sportsbook. Use promo code for 1xbet for registration form to get a 100% first time deposit welcome bonus. Enter this code in the registration form to get a 100% welcome bonus up to 130$. The customer gets a free bet, free spins or free bonus money, while the website gets more customers.