Goals: Availability

• A most common attack is “denial of service” attack.
• Attacker does not get the access but can prevent other authorized users getting access as well.

Policies

• “What is permitted”
  • For example “only course students can have read access to the these lecture notes”
• Policies are usually defined by the administrator or owner of the resource.

Mechanisms

• Mechanisms are techniques/methods to enforce a policy
• For example a “attributes” associated with a file can be changed by the owners
• Mechanism need not even be technical
  • A lost ID card application must be approved by the Dean’s office before a new one is issued.
• In computer related security, typically procedural mechanisms are used.