1. In a knowledge-based authentication (KBA) system, a method of providing a set of questions, the method comprising: receiving facts from multiple fact sources, each fact source being associated with a distinct data format; providing a set of adaptors, each adaptor being constructed and arranged to convert facts in a distinct data format with which a fact source is associated to a common data format; and generating the set of questions from the facts in the common data format, the set of questions being configured to elicit, from a user, a corresponding set of responses from which a KBA result is produced; wherein the method further comprises: storing the facts in a database when the facts have been converted to the common data format, the database including a set of entries, each entry of the set of entries being associated with a fact and including at least one identifier associated with a customer; and wherein generating the set of questions from the facts in the common data format includes: producing a ranking value associated with a candidate question, the ranking value being indicative of a likelihood that a particular response to the question implies that the user is the customer; including the candidate question in the set of questions when the ranking value is greater than a threshold value; and excluding the candidate question from the set of questions when the ranking value is less than a threshold value.