$2.$A security policy is a statement of what is and what is not allowed. A security mechanism is a method, tool, or procedure for enforcing a security policy. For each of the following situations $($a to e$),$ formulate a security policy and identify a mechanism for implementing the policy.

Example situation: Several security breaches occurred when users used passwords that are too short $($normally fewer than $5$ letters$/$digits$)$ or words that are directly from dictionary. Example Policy: Passwords should be greater than $8$ characters long and should not be found in the dictionary.

Example Mechanism: An operating system password program can be created to enforce above password policy by requiring passwords of a minimum length and preventing use of any word from the dictionary.

a$.$ One of the attacking strategies hackers often use is to guess a user's password to break into protected systems $($Don$\text{'}$t repeat example policy above$).$