Security Questions is a moodle plugin that displays a random personal question to the student to verify is the same user that was enroled in the course.
The questions are created in the "User Profile Custom Fields" section and are unlimited. The student enter the answers at the time of registration. Once logged, the student can answer the questions when in the Home page only. The questions are never displayed in the activities or resources pages.
If the student fails the question then is locked and the admin receives an email with the user locked. The number of failed attempts can be configured by the admin. The admin can list the locked students and unlock them from the user profile (Suspended account checkbox)