Abstract
Completely Automated Public Turning Test to Tell Computers and Humans Apart (CAPTCHA) is a security mechanism that is used by online communities to block spam and hacking. Today, there are a large number of sophisticated CAPTCHAs that are robust, however, most of them are unusable. This chapter describes a study to examine types and characteristics of Text CAPTCHAs used by top 50 online communities. Furthermore, the study the first of its type to develop a scale to measure usability of text CAPTCHA and to examine the relationships between dimensions of CAPTCHA and perception of usability and satisfaction with registration process in online communities. Factor analysis and equation modeling study suggests that text-based CAPTCHA can be measured on four reflective dimensions of: (1) content; (2) visual layout; (3) distortion; and (4) service in which correlate significantly to users' sanctification with online community.
TopIntroduction
CAPTCHA- Completely Automatic Public Turing test to Tell Computers and Humans Apart- is a security application that is used by many websites to avoid spamming and hacking. CAPTCHA provides a test that humans are able to solve, but computer programs cannot, to defeat websites and stop spammers and hackers. CAPTCHA test can be viewed as a function of random input that generates a challenge test and a solution. Previous research found that website users spend on average 10 seconds per CAPTCHA (Sutherland, 2012), which suggests for 200 million CAPTCHA that are solved by human users every day, more than 5000,000 hours on daily basis are lost productivity (Sutherland, 2012). CAPTCHA is developed as an instrument to limit misuse of websites that offer free services of email creation, weblogs posting, social networking, online voting, online games online banking, or chat rooms, etc. With this aim in mind, several CAPTCHAs (Boshmaf et al., 2012; Coats and Baird, 2001; Chellapilla and Simard, 2005a; Von Ahn and Blum, 2005) are developed. CAPTCHAs share a number of common characteristics: (i) automated test; (ii) publicly available; (iii) separability of test- generation and solution; and (iv) defeating attacks (Fidas et al., 2011, Swaid, 2013). A number of different techniques for generating CAPTCHAs have been developed, each satisfying the criteria of CAPTCHA test described above.
CAPTCHA types can be categorized to five main types: (i) text CAPTCHA such as reCAPTCHA and Gimby CAPTCHA (ReCaptcha, 2015); (ii) image-based CAPTCHA such as ASIRRA (Elson et al., 2007), Bongo (Bongo, 2015)and Pix (Pix, 2015) that rely on image-recognition techniques (Vikram et al., 2011); (iii) animation-based CAPTCHA; (iv) audio CAPTCHA (e.g., ReCaptcha Audio Captcha, Digg, and (v) other (e.g., mathematical functions, games, multiple choice, and cognitive based CAPTCHA) (Hernandez-Castro and Ribagorda, 2010; Yamamoto et al., 2010). Text CAPTCHA is the most common type where the user is presented with a challenge-response test in a form of numbers and letters, and user needs to strike in the right characters in the given text box. In this chapter, the author uses text CAPTCHA and CAPTCHA alternatively focusing on usability of text-based CAPTCHA that is formed of randomly generated sequence of letters and/or numbers that appear as a distorted image.
Key Terms in this Chapter
Equation Modeling: Structural equation modeling refers to a set of mathematical models, algorithms, and statistical methods that fit networks of constructs to data. SEM includes confirmatory factor analysis, path analysis, partial least squares path analysis, and latent growth modeling, among others.
CAPTCHA: An acronym for “Completely Automated Public Turing test to tell Computers and Humans Apart”. CAPTCHA is a program that protects websites against bots and hackers by generating and grading tests that humans can pass but current computer programs cannot.
User Satisfaction: The attitude of a user to the CAPTCHA Scheme adopted by the website.
Factor Analysis: Factor analysis is a statistical method for data reduction that describes variability among observed, correlated variables in terms of a potentially lower number of unobserved variables called factors.
Online Community: A virtual network of people who communicate with one another through interactive tools such as forums, discussion groups of social networking sites.
CAPTCHA Usability: Ease of use CAPTCHA scheme and solve its test.