Explanation:
Social engineering can best be mitigated through periodic security awareness training for users who may be the target of such an attempt. Implementing on-screen masking of passwords and increasing the frequency of password changes are desirable, but these will not be effective in reducing the likelihood of a successful social engineering attack. Requiring that passwords be kept secret in security policies is a good control but is not as effective as periodic security awareness programs that will alert users of the dangers posed by social engineering.