Pearson SSCP New Attempt

Kerberos is a trusted, credential-based, third-party authentication protocol that uses symmetric (secret) key cryptography to provide robust authentication to clients accessing services on a network.

Because a client's password is used in the initiation of the Kerberos request for the service protocol, password guessing can be used to impersonate a client.

Here is a nice overview of HOW Kerberos is implement as described in RFC 4556:

1. Introduction

The Kerberos V5 protocol [RFC4120] involves use of a trusted third

party known as the Key Distribution Center (KDC) to negotiate shared

session keys between clients and services and provide mutual

authentication between them.

The corner-stones of Kerberos V5 are the Ticket and the

Authenticator. A Ticket encapsulates a symmetric key (the ticket

session key) in an envelope (a public message) intended for a

specific service. The contents of the Ticket are encrypted with a

symmetric key shared between the service principal and the issuing

KDC. The encrypted part of the Ticket contains the client principal

name, among other items. An Authenticator is a record that can be

shown to have been recently generated using the ticket session key in

the associated Ticket. The ticket session key is known by the client

who requested the ticket. The contents of the Authenticator are

encrypted with the associated ticket session key. The encrypted part

of an Authenticator contains a timestamp and the client principal

name, among other items.

As shown in Figure 1, below, the Kerberos V5 protocol consists of the

following message exchanges between the client and the KDC, and the

client and the application service:

The Authentication Service (AS) Exchange

The client obtains an "initial" ticket from the Kerberos

authentication server (AS), typically a Ticket Granting Ticket

(TGT). The AS-REQ message and the AS-REP message are the request

and the reply message, respectively, between the client and the

AS.

The Ticket Granting Service (TGS) Exchange

The client subsequently uses the TGT to authenticate and request a

service ticket for a particular service, from the Kerberos

ticket-granting server (TGS). The TGS-REQ message and the TGS-REP

message are the request and the reply message respectively between

the client and the TGS.

The Client/Server Authentication Protocol (AP) Exchange

The client then makes a request with an AP-REQ message, consisting

of a service ticket and an authenticator that certifies the

client's possession of the ticket session key. The server may

optionally reply with an AP-REP message. AP exchanges typically

negotiate session-specific symmetric keys.

Usually, the AS and TGS are integrated in a single device also known

as the KDC.

+--------------+

+--------->| KDC |

AS-REQ / +-------| |

/ / +--------------+

/ / ^ |

/ |AS-REP / |

| | / TGS-REQ + TGS-REP

| | / /

| | / /

| | / +---------+

| | / /

| | / /

| | / /

| v / v

++-------+------+ +-----------------+

| Client +------------>| Application |

| | AP-REQ | Server |

| |<------------| |

+---------------+ AP-REP +-----------------+

Figure 1: The Message Exchanges in the Kerberos V5 Protocol

In the AS exchange, the KDC reply contains the ticket session key,

among other items, that is encrypted using a key (the AS reply key)

shared between the client and the KDC. The AS reply key is typically

derived from the client's password for human users. Therefore, for

human users, the attack resistance strength of the Kerberos protocol

is no stronger than the strength of their passwords.

Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 2: Access control systems (page 40).

And

HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002, chapter 4: Access Control (pages 147-151).

and

http://www.ietf.org/rfc/rfc4556.txt

Making the determination to decide what level of classification the information requires is the main responsibility of the data owner.

The data owner within classification is a person from Management who has been entrusted with a data set that belong to the company. It could be for example the Chief Financial Officer (CFO) who has been entrusted with all financial date or it could be the Human Resource Director who has been entrusted with all Human Resource data. The information owner will decide what classification will be applied to the data based on Confidentiality, Integrity, Availability, Criticality, and Sensitivity of the data.

The Custodian is the technical person who will implement the proper classification on objects in accordance with the Data Owner. The custodian DOES NOT decide what classification to apply, it is the Data Owner who will dictate to the Custodian what is the classification to apply.

NOTE:

The term Data Owner is also used within Discretionary Access Control (DAC). Within DAC it means the person who has created an object. For example, if I create a file on my system then I am the owner of the file and I can decide who else could get access to the file. It is left to my discretion. Within DAC access is granted based solely on the Identity of the subject, this is why sometimes DAC is referred to as Identity Based Access Control.

The other choices were not the best answer

Running regular backups is the responsibility of custodian.

Audit the data users is the responsibility of the auditors

Periodically check the validity and accuracy of the data is not one of the data owner responsibility

Reference(s) used for this question:

KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Page 14, Chapter 1: Security Management Practices.

equal error rate or crossover error rate (EER or CER): the rate at which both accept and reject errors are equal. The value of the EER can be easily obtained from the ROC curve. The EER is a quick way to compare the accuracy of devices with different ROC curves. In general, the device with the lowest EER is most accurate.

In the context of Biometric Authentication almost all types of detection permit a system's sensitivity to be increased or decreased during an inspection process. If the system's sensitivity is increased, such as in an airport metal detector, the system becomes increasingly selective and has a higher False Reject Rate (FRR).

Conversely, if the sensitivity is decreased, the False Acceptance Rate (FAR) will increase.

Thus, to have a valid measure of the system performance, the CrossOver Error Rate (CER) is used.

The following are used as performance metrics for biometric systems:

false accept rate or false match rate (FAR or FMR): the probability that the system incorrectly matches the input pattern to a non-matching template in the database. It measures the percent of invalid inputs which are incorrectly accepted. In case of similarity scale, if the person is imposter in real, but the matching score is higher than the threshold, then he is treated as genuine that increase the FAR and hence performance also depends upon the selection of threshold value.

false reject rate or false non-match rate (FRR or FNMR): the probability that the system fails to detect a match between the input pattern and a matching template in the database. It measures the percent of valid inputs which are incorrectly rejected.

failure to enroll rate (FTE or FER): the rate at which attempts to create a template from an input is unsuccessful. This is most commonly caused by low quality inputs.

failure to capture rate (FTC): Within automatic systems, the probability that the system fails to detect a biometric input when presented correctly.

template capacity: the maximum number of sets of data which can be stored in the system.

Reference(s) used for this question:

KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 37.

and

Wikipedia at: https://en.wikipedia.org/wiki/Biometrics

In an organization where there are frequent personnel changes, non-discretionary access control (also called Role Based Access Control) is useful because the access controls are based on the individual's role or title within the organization. You can easily configure a new employee acces by assigning the user to a role that has been predefine. The user will implicitly inherit the permissions of the role by being a member of that role.

These access permissions defined within the role do not need to be changed whenever a new person takes over the role.

Another type of non-discretionary access control model is the Rule Based Access Control (RBAC or RuBAC) where a global set of rule is uniformly applied to all subjects accessing the resources. A good example of RuBAC would be a firewall.

This question is a sneaky one, one of the choice has only one added word to it which is often. Reading questions and their choices very carefully is a must for the real exam. Reading it twice if needed is recommended.

Shon Harris in her book list the following ways of managing RBAC:

Role-based access control can be managed in the following ways:

Non-RBAC Users are mapped directly to applications and no roles are used. (No roles being used)

Limited RBAC Users are mapped to multiple roles and mapped directly to other types of applications that do not have role-based access functionality. (A mix of roles for applications that supports roles and explicit access control would be used for applications that do not support roles)

Hybrid RBAC Users are mapped to multiapplication roles with only selected rights assigned to those roles.

Full RBAC Users are mapped to enterprise roles. (Roles are used for all access being granted)

NIST defines RBAC as:

Security administration can be costly and prone to error because administrators usually specify access control lists for each user on the system individually. With RBAC, security is managed at a level that corresponds closely to the organization's structure. Each user is assigned one or more roles, and each role is assigned one or more privileges that are permitted to users in that role. Security administration with RBAC consists of determining the operations that must be executed by persons in particular jobs, and assigning employees to the proper roles. Complexities introduced by mutually exclusive roles or role hierarchies are handled by the RBAC software, making security administration easier.

Reference(s) used for this question:

KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 32.

and

Harris, Shon (2012-10-25). CISSP All-in-One Exam Guide, 6th Edition McGraw-Hill.

and

http://csrc.nist.gov/groups/SNS/rbac/