Section: Access Control
Explanation/Reference:
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

Explanation/Reference:
Rijndael. Rijndael is the new approved method of encrypting sensitive but unclassified information for the U.S. government. It has been accepted by and is also widely used in the public arena as well. It has low memory requirements and has been constructed to easily defend against timing attacks.
The following answers are incorrect: Twofish. Twofish was among the final candidates chosen for AES, but was not selected.
Serpent. Serpent was among the final candidates chosen for AES, but was not selected.
RC6. RC6 was among the final candidates chosen for AES, but was not selected.
The following reference(s) were/was used to create this question:
ISC2 OIG, 2007 p. 622, 629-630
Shon Harris AIO, v.3 p 247-250

Explanation/Reference:
Computer worms are also known as Network Mobile Code, or a virus-like bit of code that can replicate itself over a network, infecting adjacent computers.
A computer worm is a standalone malware computer program that replicates itself in order to spread to other computers. Often, it uses a computer network to spread itself, relying on security failures on the target computer to access it. Unlike a computer virus, it does not need to attach itself to an existing program. Worms almost always cause at least some harm to the network, even if only by consuming bandwidth, whereas viruses almost always corrupt or modify files on a targeted computer.
A notable example is the SQL Slammer computer worm that spread globally in ten minutes on January 25,
2003. I myself came to work that day as a software tester and found all my SQL servers infected and actively trying to infect other computers on the test network.
A patch had been released a year prior by Microsoft and if systems were not patched and exposed to a
376 byte UDP packet from an infected host then system would become compromised.
Ordinarily, infected computers are not to be trusted and must be rebuilt from scratch but the vulnerability could be mitigated by replacing a single vulnerable dll called sqlsort.dll.
Replacing that with the patched version completely disabled the worm which really illustrates to us the importance of actively patching our systems against such network mobile code.
The following answers are incorrect:
- Rootkit: Sorry, this isn't correct because a rootkit isn't ordinarily classified as network mobile code like a worm is. This isn't to say that a rootkit couldn't be included in a worm, just that a rootkit isn't usually classified like a worm. A rootkit is a stealthy type of software, typically malicious, designed to hide the existence of certain processes or programs from normal methods of detection and enable continued privileged access to a computer. The term rootkit is a concatenation of "root" (the traditional name of the privileged account on Unix operating systems) and the word "kit" (which refers to the software components that implement the tool). The term "rootkit" has negative connotations through its association with malware.
- Adware: Incorrect answer. Sorry but adware isn't usually classified as a worm. Adware, or advertising- supported software, is any software package which automatically renders advertisements in order to generate revenue for its author. The advertisements may be in the user interface of the software or on a screen presented to the user during the installation process. The functions may be designed to analyze which Internet sites the user visits and to present advertising pertinent to the types of goods or services featured there. The term is sometimes used to refer to software that displays unwanted advertisements.
- Logic Bomb: Logic bombs like adware or rootkits could be spread by worms if they exploit the right service and gain root or admin access on a computer.
The following reference(s) was used to create this question:
The CCCure CompTIA Holistic Security+ Tutorial and CBT
and
http://en.wikipedia.org/wiki/Rootkit
and
http://en.wikipedia.org/wiki/Computer_worm
and
http://en.wikipedia.org/wiki/Adware

Section: Network and Telecommunications
Explanation/Reference:
Communications security and techniques are the best area for addressing this objective.
"Information security management and techniques" is incorrect. While the overall information security program would include this objective, communications security is the more specific and better answer.
"Client security management and techniques" is incorrect. While client security plays a part in this overall objective, communications security is the more specific and better answer.
"Server security management and techniques" is incorrect. While server security plays a part in this overall objective, communications security is the more specific and better answer.
References:
CBK, p. 408

Section: Network and Telecommunications
Explanation/Reference:
Bridges are simple, protocol-dependent networking devices that are used to connect two or more homogeneous LANs to form an extended LAN.
A bridge does not change the contents of the frame being transmitted but acts as a relay.
A gateway is designed to reduce the problems of interfacing any combination of local networks that employ different level protocols or local and long-haul networks.
A router connects two networks or network segments and may use IP to route messages.
Firewalls are methods of protecting a network against security threats from other systems or networks by centralizing and controlling access to the protected network segment.
Source: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002, chapter 7:
Telecommunications and Network Security (page 397).