Security and Communication Networks / 2017 / Article / Tab 1

Review Article

A Survey on Breaking Technique of Text-Based CAPTCHA

Table 1

Typical types of text-based CAPTCHA and their features.


Solid CAPTCHADiscuz!Character independent, texture background, some interference
SlashdotA large number of interference lines and noise points
GimpyMultiple strings, overlap, distortion
GoogleUnfixed length, distortion, adhesion
MicrosoftDouble-string, unfixed length, uneven thickness, tilting, adhesion

Hollow CAPTCHAQQHollow, shadows, interference shapes
SinaHollow, adhesion, interference lines
YandexHollow, virtual contours, distortion, adhesion, interference lines

Three-dimensional CAPTCHAScihubHollow, shadows, interference lines, noise points
TeabagGrids, protrusion, distortion, background and character blending
ParcColorful, shadow, rotation, zoom
Special characters

Animation CAPTCHAProgram generatingMultiple characters jumping
HcaptchaMultilayer character images blinking transformation