A hacker is attempting to gain access to a target inside a business. After trying several methods, he gets frustrated and starts a denial of service attack against a server attached to the goal.
Availability: Denial of Service attacks against the availability of the system. Regardless of whatever else the hacker has tried to accomplish against the machine, a successful Dos attack removes the availability of the machine. Remember, availability refers to the communications systems and data being ready for use when legitimate users need them.
Many methods are used for availability, depending on whether the discussion is about a system, network resource, or the data itself. However, they all attempt to ensure one thing. when the system or data is needed, it can be accessed by the appropriate personnel. Attacks against availability always fall into the denial of service realm.