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Abstract –Due to the growth of the internet in our life and its importance in all our everyday activities , including occupational and educational ones .We should also keep in mind that it harbours a negative aspect , as it brings security problems. Hence CAPTCHAs are used for making systems more secure. The major role of CAPTCHA is to prevent robotic bot (spam) form surrender or prove user personality. Using a pattern-matching algorithm is necessary for the user for comparison by receiving signs founded in similar matches. This method makes it difficult to get a forbidden access to data, since malicious bot is to spy out signs in the image. This mechanism implements actions on the attitude of user gesticulation which makes it distinguishable and secure. Human-Computer Interaction i.e. interaction between computer and individual is made to make it easy in understand human language .On other words, Human-computer Interaction focuses on the study of interfaces between computer and human. This paper presents a comprehensive study of various different types of CAPTCHA, the ones good in securing webpages. It also discusses the strengths and weaknesses of each one. Moreover, its importance in discerning the user’s individuality, the behavior of humans, and bots and the paper will illustrate some CAPTCHAs mechaniits and impairments which allows hackers to break .In addition, is necessary to take into consideration the approaches of building a good CAPTCHA.

CAPTCHA , Bot programs, Hackers, spammer, Scrapers, online social network.

"A comprehensive Study for Different Types of CAPTCHA Methods and Various Attacks", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.8, Issue 6, page no.e54-e64, June-2021, Available :http://www.jetir.org/papers/JETIR2106561.pdf

"A comprehensive Study for Different Types of CAPTCHA Methods and Various Attacks", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.8, Issue 6, page no. ppe54-e64, June-2021, Available at : http://www.jetir.org/papers/JETIR2106561.pdf