CISSP Practice

In Kerberos two items need to prove authentication. The first is the ticket and the second is the authenticator. The ticket consists of the requested server name, the client name, the address of the client, the time the ticket was issued, the lifetime of the ticket, the session key to be used between the client and the server, and some other fields. The ticket is encrypted using the server’s secret key and thus cannot be correctly decrypted by the user. If the server can properly decrypt the ticket when the client presents it and if the client presents the authenticator encrypted using the session key contained in the ticket, the server can have confidence in the user’s identity. The authenticator contains the client name, address, current time, and some other fields. The authenticator is encrypted by the client using the session key shared with the server. The authenticator provides a time-validation for the credential. If a user possesses both the proper credential and the authenticator encrypted with the correct session key and presents these items within the lifetime of the ticket, then the user’s identity can be authenticated.

Confidentiality is incorrect because it ensures that data is disclosed to only authorized subjects. Integrity is incorrect because it is the property that an object is changed only in a specified and authorized manner. Availability is incorrect because it is the property that a given resource will be usable during a given time period.

251. What is the major advantage of a single sign-on?

a. It reduces management work.

b. It is a convenience for the end user.

c. It authenticates a user once.

d. It provides a centralized administration.

251. b. Under a single sign-on (SSO), a user can authenticate once to gain access to multiple applications that have been previously defined in the security system. The SSO system is convenient for the end user in that it provides fewer areas to manage when compared to multiple sign-on systems, but SSO is risky. Many points of failure exist in multiple sign-on systems as they are inconvenient for the end user because of many areas to manage.

252. Kerberos can prevent which one of the following attacks?

a. Tunneling attack

b. Playback attack

c. Destructive attack

d. Process attack

252. b. In a playback (replay) attack, messages received from something or from somewhere are replayed back to it. It is also called a reflection attack. Kerberos puts the time of day in the request to prevent an eavesdropper from intercepting the request for service and retransmitting it from the same host at a later time.

A tunneling attack attempts to exploit a weakness in a system that exists at a level of abstraction lower than that used by the developer to design the system. For example, an attacker might discover a way to modify the microcode of a processor used when encrypting some data, rather than attempting to break the system’s encryption algorithm.

Destructive attacks damage information in a fashion that denies service. These attacks can be prevented by restricting access to critical data files and protecting them from unauthorized users.

In process attacks, one user makes a computer unusable for others that use the computer at the same time. These attacks are applicable to shared computers.

253. From an access control point of view, which of the following are examples of history-based access control policies?

1. Role-based access control

2. Workflow policy

3. Rule-based access control

4. Chinese Wall policy

a. 1 and 2

b. 1 and 3

c. 2 and 4

d. 3 and 4

253. c. History-based access control policies are defined in terms of subjects and events where the events of the system are specified as the object access operations associated with activity at a particular security level. This assumes that the security policy is defined in terms of the sequence of events over time, and that the security policy decides which events of the system are permitted to ensure that information does not flow in an unauthorized manner. History-based access control policies are not based on standard access control mechanism but based on practical applications. In the history-based access control policies, previous access events are used as one of the decision factors for the next access authorization. The workflow and the Chinese Wall policies are examples of history-based access control policies.

254. Which of the following is most commonly used in the implementation of an access control matrix?

a. Discretionary access control

b. Mandatory access control

c. Access control list

d. Logical access control