CAPTCHAs, are those needed anymore?

For more than a decade, CAPTCHAs are around to enhance the security level of a broad range of web-based activities such as ecommerce, online polls, etc. Although, the literature of the topic is a fertile one and there are many studies in which different types of such tests presented; there are several issues that greatly question the efficiency of CAPTCHAs, such as usability and accessibility problems. In this regard, efforts made to improve different aspects of CAPTCHAs and even some alternatives have been proposed. Nonetheless, it can be said that the CAPTCHA, despite its applications and benefits, is not a popular phenomena among the web users. Moreover, in some cases the disadvantages of using CAPTCHAs surpasses its advantages. Such issues prompt a critical question that perhaps this is the time for retiring CAPTCHAs. This is what is studied in this paper from different aspects to provide a current status report of the CAPTCHA and its alternative solutions.