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.

TypeExampleSourceFeatures

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