The WebCaptcha™ control provides three basic types of protection against automated form submissions:
Captcha ProtectionMode – this is the default mode. In this mode the user has to input randomly generated characters, word/s or an answer to a predefined question. To see how to specify one of these, see the Dictionary Modes topic.
Invisible Input Field ProtectionMode – in this mode the control renders an additional input element, which is invisible to the user. So if any editing is performed to this field, it is assumed this has been done by a bot and the validation will fail.
Form Submission Timeout ProtectionMode – in this mode the control will count the seconds defined by the FormSubmissionTimeoutSeconds property. If the form is submitted before these seconds pass, the validation will fail.