The reference monitor refers to abstract machine that mediates all access to objects by subjects.
This question is asking for the concept that governs access by subjects to objects, thus the reference monitor is the best answer. While the security kernel is similar in nature, it is what actually enforces the concepts outlined in the reference monitor.
In operating systems architecture a reference monitor concept defines a set of design requirements on a reference validation mechanism, which enforces an access control policy over subjects’ (e.g., processes and users) ability to perform operations (e.g., read and write) on objects (e.g., files and sockets) on a system. The properties of a reference monitor are:
The reference validation mechanism must always be invoked (complete mediation). Without this property, it is possible for an attacker to bypass the mechanism and violate the security policy.
The reference validation mechanism must be tamperproof (tamperproof). Without this property, an attacker can undermine the mechanism itself so that the security policy is not correctly enforced. The reference validation mechanism must be small enough to be subject to analysis and tests, the completeness of which can be assured (verifiable). Without this property, the mechanism might be flawed in such a way that the policy is not enforced.
For example, Windows 3.x and 9x operating systems were not built with a reference monitor, whereas the Windows NT line, which also includes Windows 2000 and Windows XP, was designed to contain a reference monitor, although it is not clear that its properties (tamperproof, etc.) have ever been independently verified, or what level of computer security it was intended to provide.
The claim is that a reference validation mechanism that satisfies the reference monitor concept will correctly enforce a system’s access control policy, as it must be invoked to mediate all security- sensitive operations, must not be tampered, and has undergone complete analysis and testing to verify correctness. The abstract model of a reference monitor has been widely applied to any type of system that needs to enforce access control, and is considered to express the necessary and sufficient properties for any system making this security claim.
According to Ross Anderson, the reference monitor concept was introduced by James Anderson in an influential 1972 paper.
Systems evaluated at B3 and above by the Trusted Computer System Evaluation Criteria (TCSEC) must enforce the reference monitor concept.
The reference monitor, as defined in AIO V5 (Harris) is: “an access control concept that refers to an abstract machine that mediates all access to objects by subjects.” The security kernel, as defined in AIO V5 (Harris) is: “the hardware, firmware, and software elements of a trusted computing based (TCB) that implement the reference monitor concept. The kernel must mediate all access between subjects and objects, be protected from modification, and be verifiable as correct.” The trusted computing based (TCB), as defined in AIO V5 (Harris) is: “all of the protection mechanisms within a computer system (software, hardware, and firmware) that are responsible for enforcing a security policy.” The security domain, “builds upon the definition of domain (a set of resources available to a subject) by adding the fact that resources withing this logical structure (domain) are working under the same security policy and managed by the same group.” The following answers are incorrect:
“The security kernel” is incorrect. One of the places a reference monitor could be implemented is in the security kernel but this is not the best answer.
“The trusted computing base” is incorrect. The reference monitor is an important concept in the TCB but this is not the best answer.
“The security domain is incorrect.” The reference monitor is an important concept in the security domain but this is not the best answer.

Section: Access Control
Explanation/Reference:
The Bell-LaPadula model is a formal model dealing with confidentiality.
The Bell-LaPadula Model (abbreviated BLP) is a state machine model used for enforcing access control in government and military applications. It was developed by David Elliott Bell and Leonard J. LaPadula, subsequent to strong guidance from Roger R. Schell to formalize the U.S. Department of Defense (DoD) multilevel security (MLS) policy. The model is a formal state transition model of computer security policy that describes a set of access control rules which use security labels on objects and clearances for subjects.
Security labels range from the most sensitive (e.g.”Top Secret”), down to the least sensitive (e.g.,
“Unclassified” or “Public”).
The Bell-LaPadula model focuses on data confidentiality and controlled access to classified information, in contrast to the Biba Integrity Model which describes rules for the protection of data integrity. In this formal model, the entities in an information system are divided into subjects and objects.
The notion of a “secure state” is defined, and it is proven that each state transition preserves security by moving from secure state to secure state, thereby inductively proving that the system satisfies the security objectives of the model. The Bell-LaPadula model is built on the concept of a state machine with a set of allowable states in a computer network system. The transition from one state to another state is defined by transition functions.
A system state is defined to be “secure” if the only permitted access modes of subjects to objects are in accordance with a security policy. To determine whether a specific access mode is allowed, the clearance of a subject is compared to the classification of the object (more precisely, to the combination of classification and set of compartments, making up the security level) to determine if the subject is authorized for the specific access mode.
The clearance/classification scheme is expressed in terms of a lattice. The model defines two mandatory access control (MAC) rules and one discretionary access control (DAC) rule with three security properties:
The Simple Security Property – a subject at a given security level may not read an object at a higher security level (no read-up).
The -property (read “star”-property) – a subject at a given security level must not write to any object at a lower security level (no write-down). The -property is also known as the Confinement property.
The Discretionary Security Property – use of an access matrix to specify the discretionary access control.
The following are incorrect answers:
Accountability is incorrect. Accountability requires that actions be traceable to the user that performed them and is not addressed by the Bell-LaPadula model.
Integrity is incorrect. Integrity is addressed in the Biba model rather than Bell-Lapadula.
Availability is incorrect. Availability is concerned with assuring that data/services are available to authorized users as specified in service level objectives and is not addressed by the Bell-Lapadula model.
References:
CBK, pp. 325-326
AIO3, pp. 279 – 284
AIOv4 Security Architecture and Design (pages 333 – 336)
AIOv5 Security Architecture and Design (pages 336 – 338)
Wikipedia at https://en.wikipedia.org/wiki/Bell-La_Padula_model

Explanation/Reference:
A digital signature directly addresses both confidentiality and integrity of the CIA triad. It does not directly address availability, which is what denial-of-service attacks.
The other answers are not correct because:
“nonrepudiation” is not correct because a digital signature can provide for nonrepudiation.
“authentication” is not correct because a digital signature can be used as an authentication mechanism
“data integrity” is not correct because a digital signature does verify data integrity (as part of nonrepudiation)
References:
Official ISC2 Guide page: 227 & 265
All in One Third Edition page: 648

The answer: Preventive/Administrative Pairing: These mechanisms include organizational policies and procedures, pre-employment background checks, strict hiring practices, employment agreements, friendly and unfriendly employee termination procedures, vacation scheduling, labeling of sensitive materials, increased supervision, security awareness training, behavior awareness, and sign-up procedures to obtain access to information systems and networks.

Explanation/Reference:
Twisted Pair cables currently have two categories in common usage. CAT3 and CAT5.
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 72.

The keyword is ‘ MOST CRITICAL ‘ and the correct answer is ‘ Management Support ‘ as the management must be convinced of its necessity and that’s why a business case must be made. The decision of how a company should recover from any disaster is purely a business decision and should be treated as so.
The other answers are incorrect because :
Security policy is incorrect as it is not the MOST CRITICAL piece.
Availability of backup information processing facilities is incorrect as this comes once the organization has BCP Plans in place and for a BCP Plan , management support must be there.
Staff training comes after the plans are in place with the support from management. Reference : Shon Harris , AIO v3 , Chapter-9: Business Continuity Planning , Page : 697.

A live disaster test or Full interruption test is an actual simulation of the Disaster Recovery Plan.
All operations are shut down and brought back online at the alternate site. This test poses the biggest threat to an organization and should not be performed until a successful Parallell Test has been conducted.
1. A Checklist test would be conducted where each of the key players will get a copy of the plan and they read it to make sure it has been properly developed for the specific needs of their departments.
2. A Structure Walk Through would be conducted next. This is when all key players meet together in a room and they walk through the test together to identify shortcoming and dependencies between department.
3. A simulation test would be next. In this case you go through a disaster scenario up to the point where you would move to the alternate site. You do not move to the alternate site and you learn from your mistakes and you improve the plan. It is the right time to find shortcomings.
4. A Parallell Test would be done. You go through a disaster scenario. You move to the alternate site and you process from both sites simultaneously.
5. A full interruption test would be conducted. You move to the alternate site and you resume processing at the alternate site.
The following answers are incorrect:
Restore all files in preparation for the test. Is incorrect because you would restore the files at the alternate site as part of the test not in preparation for the test.
Document expected findings. Is incorrect because it is not the best answer. Documenting the expected findings won’t help if you have not performed tests prior to a Full interruption test or live disaster test.
Arrange physical security for the test site. Is incorrect because it is not the best answer. why physical security for the test site is important if you have not performed a successful structured walk-through prior to performing a Full interruption test or live disaster test you might have some unexpected and disasterous results.

Section: Risk, Response and Recovery
Explanation/Reference:
The Business Impact Analysis (BIA) identifies time-critical aspects of the critical business processes, and determines their maximum tolerable downtime. The BIA helps to Identify organization functions, the capabilities of each organization unit to handle outages, and the priority and sequence of functions and applications to be recovered, identify resources required for recovery of those areas and interdependencies In performing the Business Impact Analysis (BIA) it is very important to consider what the dependencies are.
You cannot bring a system up if it depends on another system to be operational. You need to look at not only internal dependencies but external as well. You might not be able to get the raw materials for your business so dependencies are very important aspect of a BIA.
The BIA committee will not truly understand all business processes, the steps that must take place, or the resources and supplies these processes require. So the committee must gather this information from the people who do know- department managers and specific employees throughout the organization. The committee starts by identifying the people who will be part of the BIA data-gathering sessions. The committee needs to identify how it will collect the data from the selected employees, be it through surveys, interviews, or workshops. Next, the team needs to collect the information by actually conducting surveys, interviews, and workshops. Data points obtained as part of the information gathering will be used later during analysis. It is important that the team members ask about how different tasks- whether processes, transactions, or services, along with any relevant dependencies- get accomplished within the organization.
The following answers are incorrect:
composition This is incorrect because it is not the best answer. While the make up of business may be important, if you have not determined the dependencies first you may not be able to bring the critical business processes to a ready state or have the materials on hand that are needed.
priorities This is incorrect because it is not the best answer. While the priorities of processes are important, if you have not determined the dependencies first you may not be able to bring the critical business processes to a ready state or have the materials on hand that are needed.
service levels This is incorrect because it is not the best answer. Service levels are not as important as dependencies.
Reference(s) used for this question:
Schneiter, Andrew (2013-04-15). Official (ISC)2 Guide to the CISSP CBK, Third Edition : Business Continuity and Disaster Recovery Planning (Kindle Locations 188-191). . Kindle Edition.
and
Harris, Shon (2012-10-25). CISSP All-in-One Exam Guide, 6th Edition (Kindle Locations 18562-18568).
McGraw-Hill. Kindle Edition.

Explanation/Reference:
Today implementation of fast, accurate, reliable, and user-acceptable biometric identification systems are already under way. Because most identity authentication takes place when a people are fully clothed (neck to feet and wrists), the parts of the body conveniently available for this purpose are hands, face, and eyes.
From: TIPTON, Harold F. & KRAUSE, MICKI, Information Security Management Handbook, 4th Edition, Volume 1, Page 7.

Section: Security Operation Adimnistration
Explanation/Reference:
Polyinstantiation enables a relation to contain multiple tuples with the same primary keys with each instance distinguished by a security level. When this information is inserted into a database, lower-level subjects need to be restricted from this information. Instead of just restricting access, another set of data is created to fool the lower-level subjects into thinking that the information actually means something else.
Source: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002, chapter 11:
Application and System Development (page 727).

security awareness training is to modify employees behaviour
and attitude towards towards enterprise’s security posture.
Security-awareness training is performed to modify employees’ behavior and attitude
toward security. This can best be achieved through a formalized process of security-
awareness training.
It is used to increase the overall awareness of security throughout the company. It is
targeted to every single employee and not only to one group of users.
Unfortunately you cannot apply a patch to a human being, the only thing you can do is to
educate employees and make them more aware of security issues and threats. Never
underestimate human stupidity.
Reference(s) used for this question:
TIPTON, Hal, (ISC)2, Introduction to the CISSP Exam presentation.
also see:
Harris, Shon (2012-10-18). CISSP All-in-One Exam Guide, 6th Edition (p. 130). McGraw-
Hill. Kindle Edition.

Section: Cryptography
Explanation/Reference:
SSL use public-key cryptography to secure session key, while the session key (secret key) is used to secure the whole session taking place between both parties communicating with each other.
The SSL protocol was originally developed by Netscape. Version 1.0 was never publicly released; version 2.0 was released in February 1995 but “contained a number of security flaws which ultimately led to the design of SSL version 3.0.” SSL version 3.0, released in 1996, was a complete redesign of the protocol produced by Paul Kocher working with Netscape engineers Phil Karlton and Alan Freier.
All of the other answers are incorrect

The primary objective of proper separation of duties is to ensure that one person acting alone cannot compromise the company’s security in any way. A proper separation of duties does not prevent employees from disclosing information, nor does it ensure that access controls are in place or that audit trails are not tampered with. Source: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002, Chapter 12: Operations Security (Page 808).

A stream cipher treats the message as a stream of bits or bytes and performs mathematical functions on them individually. The key is a random value input into the stream cipher, which it uses to ensure the randomness of the keystream data. They are more suitable for hardware implementations, because they encrypt and decrypt one bit at a time. They are intensive because each bit must be manipulated, which works better at the silicon level. Block ciphers operate a the block level, dividing the message into blocks of bits. Cipher Block chaining (CBC) and Electronic Code Book (ECB) are operation modes of DES, a block encryption algorithm. Source: WALLHOFF, John, CBK#5 Cryptography (CISSP Study Guide), April 2002 (page 2).

The answer:
Call back Systems; Callback systems provide access protection by calling back the number of a previously authorized location, but this control can be compromised by call forwarding.

Explanation/Reference:
An Intrusion Detection System (IDS) is a system that is used to monitor network traffic or to monitor host audit logs in order to determine if any violations of an organization’s system security policy have taken place.
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 48.

Section: Network and Telecommunications
Explanation/Reference:
All the previous protocols operate at the transport layer except for Secure HTTP (S-HTTP), which operates at the application layer. S-HTTP has been replaced by SSL and TLS.
As it is very well explained in the Shon Harris book:
The transport layer receives data from many different applications and assembles the data into a stream to be properly transmitted over the network. The main protocols that work at this layer are TCP, UDP, Secure Sockets Layer (SSL), and Sequenced Packet Exchange (SPX).
NOTE:
Different references can place specific protocols at different layers. For example, many references place the SSL protocol in the session layer, while other references place it in the transport layer. It is not that one is right or wrong. The OSI model tries to draw boxes around reality, but some protocols straddle the different layers.
SSL is made up of two protocols- one works in the lower portion of the session layer and the other works in the transport layer.
For purposes of the CISSP exam, SSL resides in the transport layer.
Reference(s) used for this question:
Harris, Shon (2012-10-18). CISSP All-in-One Exam Guide, 6th Edition (p. 526). McGraw-Hill. Kindle Edition.

Echo replies outbound should be dropped, not allowed. There is no reason for any internet users to send ICMP ECHO Request to your interal hosts from the internet. If they wish to find out if a service is available, they can use a browser to connect to your web server or simply send an email if they wish to test your mail service.
Echo replies outbound could be used as part of the SMURF amplification attack where someone will send ICMP echo requests to gateways broadcast addresses in order to amplify the request by X number of users sitting behind the gateway.
By allowing inbound echo requests and outbound echo replies, it makes it easier for attackers to learn about the internal network as well by performing a simply ping sweep. ICMP can also be used to find out which host has been up and running the longest which would indicates which patches are missing on the host if a critical patch required a reboot.
ICMP can also be use for DDoS attacks, so you should strictly limit what type of ICMP traffic would be allowed to flow through your firewall.
On top of all this, tools such as LOKI could be use as a client-server application to transfer files back and forward between the internat and some of your internal hosts. LOKI is a client/server program published in the online publication Phrack . This program is a working proof-of-concept to demonstrate that data can be transmitted somewhat secretly across a network by hiding it in traffic that normally does not contain payloads. The example code can tunnel the equivalent of a Unix RCMD/RSH session in either ICMP echo request (ping) packets or UDP traffic to the DNS port. This is used as a back door into a Unix system after root access has been compromised.
Presence of LOKI on a system is evidence that the system has been compromised in the past.
The outbound echo request and inbound echo reply allow internal users to verify connectivity with external hosts.
The following answers are incorrect:
Allow echo request outbound The outbound echo request and inbound echo reply allow internal users to verify connectivity with external hosts.
Drop echo request inbound There is no need for anyone on the internet to attempt pinging your internal hosts.
Allow echo reply inbound The outbound echo request and inbound echo reply allow internal users to verify connectivity with external hosts.

Integrity refers to the protection of information from unauthorized modification or deletion.
Confidentiality is incorrect. Confidentiality refers to the protection of information from unauthorized disclosure.
Availability is incorrect. Availability refers to the assurance that information and services will be available to authorized users in accordance with the service level objective.
Auditability is incorrect. Auditability refers to the ability to trace an action to the identity that performed it and identify the date and time at which it occurred.