KT.UI Captcha library owns a set of excellent controls and composite features that make it be the market-leading captcha user interface control. It has been dedicating to offering users the comprehensive and easy to use captcha user interface controls.

In the tutorial page of KT.UI Captcha Product overview, we have talked about the major features and benefits that PerCaptcha Control owns and provides. One of outstanding features is the advanced and strict captcha protection modes. In following text, we are going to discuss these various captcha protection modes with users in details. Thus, users can get well informed of the captcha processing concept and develop your capture user interface better.

There are two major solutions for protection against automated form submissions by using KT.UI Captcha control for ASP.NET.

• Image with modified symbols. This is the most commonly used and also most scured captcha protection strategy. The image symbols are displayed in a form, and the user is required to input the symbols in a textbox. Here is the concept: if the input symbols are correct, the captcha component configures that the user is not a robot because it is not yet possible for robots to identify and input distorted symbols. There is a set of properties that characterize the image: noise factors, image, text, captcha session expiration time and captcha error message to be displayed if the entered value was incorrect.
• Automatic robots discovery - this solution needs to judge whether the input comes from a robot or not based on the predefined rules. This strategy is not 100% secure and some sophisticated robots may pass it. You can decide to use which predefined rules. For this strategy, two implemented rules that could be applied either separately or simultaneously:
• Minimum form submission time - the presumption is simple to understand, that is a human cannot input the fields in a form correctly for a time less than 3 seconds (this is set by default, and could be modified). Thus, if the time for submission is less than 3 seconds, it is assumed that the executor is a robot.
• Invisible textbox in the form - this rule requires the insertion of a textbox which is not visible when the form is styled. If the textbox is detected by a robot and certain data is entered, then, we can consider the executor to be a robot.