ESP can provide partial traffic flow confidentiality by padding the payload to hide the actual length of the data. Padding can also be used to align the payload with the encryption algorithm's block size. Padding is not used for access control, protection against replay attack, or data origin authentication. References: 1, p.
1009; 2, p. 29

Explanation/Reference:
Explanation:
Preaction systems are similar to dry pipe systems in that the water is not held in the pipes, but is released when the pressurized air within the pipes is reduced. Once this happens, the pipes are filled with water, but it is not released right away. A thermal-fusible link on the sprinkler head has to melt before the water is released. The purpose of combining these two techniques is to give people more time to respond to false alarms or to small fires that can be handled by other means. Putting out a small fire with a handheld extinguisher is better than losing a lot of electrical equipment to water damage. These systems are usually used only in data processing environments rather than the whole building, because of the higher cost of these types of systems.
Incorrect Answers:
B: Wet pipe systems always contain water in the pipes and are usually discharged by temperature control- level sensors. This type is not the most recommended water system for a computer room. Therefore, this answer is incorrect.
C: In dry pipe systems, the water is not actually held in the pipes. The water is contained in a "holding tank" until it is released. This type is not the MOST recommended water system for a computer room. Therefore, this answer is incorrect.
D: A deluge system has its sprinkler heads wide open to allow a larger volume of water to be released in a shorter period. Because the water being released is in such large volumes, these systems are usually not used in data processing environments. This type is not the most recommended water system for a computer room. Therefore, this answer is incorrect.
References:
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, p. 474-475

The most appropriate action when reusing media that contains sensitive data is to sanitize the media.
Sanitization is the process of removing or destroying all data from the media in such a way that it cannot be recovered by any means. Sanitization can be achieved by various methods, such as overwriting, degaussing, or physical destruction. Sanitization ensures that the sensitive data is not exposed or compromised when the media is reused or disposed of. Erase, encrypt, and degauss are not the most appropriate actions when reusing media that contains sensitive data, although they may be related or useful steps. Erase is the process of deleting data from the media by using the operating system or application commands or functions. Erase does not guarantee that the data is completely removed from the media, as it may leave traces or remnants that can be recovered by using special tools or techniques. Encrypt is the process of transforming data into an unreadable form by using a cryptographic algorithm and a key. Encrypt can protect the data from unauthorized access or disclosure, but it does not remove the data from the media. Encrypt also requires that the key is securely managed and stored, and that the encryption algorithm is strong and reliable. Degauss is the process of applying a strong magnetic field to the media to erase or scramble the data. Degauss can effectively sanitize magnetic media, such as hard disks or tapes, but it does not work on optical media, such as CDs or DVDs.
Degauss also renders the media unusable, as it destroys the servo tracks and the firmware that are needed for the media to function properly.

The correct answer is "The best possible safeguard should always be implemented, regardless of cost.". Performing a cost-benefit analysis of the
proposed safeguard before implementation is vital. The level of security afforded could easily outweigh the value of a proposed safeguard.
Other factors need to be considered in the safeguard selection
process, such as accountability, auditability, and the level of manual
operations needed to maintain or operate the safeguard.

Role-Based Access Control (RBAC) is the type of access control that determines the authorization to resources based on predefined job titles within an organization. RBAC is a model of access control that assigns roles to users based on their functions, responsibilities, or qualifications, and grants permissions to resources based on the roles. RBAC simplifies the management and administration of access control, as it reduces the complexity and redundancy of assigning permissions to individual users or groups. RBAC also enhances the security and compliance of access control, as it enforces the principle of least privilege and the separation of duties.
References: CISSP All-in-One Exam Guide, Eighth Edition, Chapter 5: Identity and Access Management, page 203. Free daily CISSP practice questions, Question 4.