Techniques to provide evidence-based dynamic scoring to limit guesses in knowledge based authentication are disclosed herein. In some aspects, an authenticator may receive an input from a user in response to a presentation of a personal question that enables user access to a restricted resource. The authenticator may determine that the input is not equivalent to a stored value, and thus is an incorrect input. The authenticator may then determine whether the input is similar to a previous input received from the user. A score may be assigned to the input. When the input is determined to be similar to the previous input, the score may be reduced. Another request for an input may be transmitted by the authenticator when a sum of the score and any previous scores of the session is less than a threshold.