A method of dynamically generating a security question for accessing a resource. The method comprises monitoring a behavior of said user during a monitoring period to identify automatically a deviation from a behavioral pattern indicative of repetitive behavior of a user, automatically generating a security question responded to by an indication of said deviation, receiving a user input inputted by a user in response to a presentation of said security question and said deviation, and authenticating, after said monitoring period, an access to a resource according to a match between said user input and said deviation.