Explanation/Reference:
The correct answer is "56". This is actually a bit of a trick question, since the actual key length is 64 bits.
However, every eighth bit is ignored because it is used for parity. This makes the "effective length of the key" that the question actually asks for 56 bits.
The other answers are not correct because:
168 - This is the number of effective bits in Triple DES (56 times 3).
128 - Many encryption algorithms use 128 bit key, but not DES. Note that you may see 128 bit encryption referred to as "military strength encryption" because many military systems use key of this length.
64 - This is the actual length of a DES encryption key, but not the "effective length" of the DES key.
Reference:
Official ISC2 Guide page: 238
All in One Third Edition page: 622

Section: Network and Telecommunications
Explanation/Reference:
The User Datagram Protocol (UDP) is implemented at the host-to-host transport layer, not at the internet layer.
Protocol at what layer?
Ensure you are familiar with both the OSI model and the DoD TCP/IP model as well. You need to know how to contrast the two side by side and what are the names being used on both side. Below you have a graphic showing the two and how things maps between the two as well as some of the most common protcolos found at each of the layers:
Protocols at what layers of the DoD TCP/IP model

Graphic from http://technet.microsoft.com/en-us/library/cc958821.aspx
The following are incorrect answers:
All of the other protocols sit at the Internet Layer of the TCP/IP model.
NOTE:
Some reference are calling the Transport layer on the DoD model Host-to-Host.
Reference(s) used for this question:
Shon Harris, CISSP All In One (AIO), 6th edition , Telecommunication and Network Security, Page 518,534 and KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 3: Telecommunications and Network Security (page 85).
and
Microsoft Technet at http://technet.microsoft.com/en-us/library/cc958821.aspx

Section: Network and Telecommunications
Explanation/Reference:
One the most secure implementations of firewall architectures is the screened-subnet firewall. It employs two packet-filtering routers and a bastion host. Like a screened host firewall, this firewall supports both packet- filtering and proxy services.
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 3: Telecommunications and Network Security (page
93).

Section: Cryptography
Explanation/Reference:
Named after its inventors Ron Rivest , Adi Shamir and Leonard Adleman is based on the difficulty of factoring large prime numbers.
Factoring a number means representing it as the product of prime numbers. Prime numbers, such as 2, 3, 5,
7, 11, and 13, are those numbers that are not evenly divisible by any smaller number, except 1. A non-prime, or composite number, can be written as the product of smaller primes, known as its prime factors. 665, for example is the product of the primes 5, 7, and 19. A number is said to be factored when all of its prime factors are identified. As the size of the number increases, the difficulty of factoring increases rapidly.
The other answers are incorrect because:
El Gamal is based on the discrete logarithms in a finite field.
Elliptic Curve Cryptosystems (ECCs) computes discrete logarithms of elliptic curves.
International Data Encryption Algorithm (IDEA) is a block cipher and operates on 64 bit blocks of data and is a SYMMETRIC algorithm.
Reference : Shon Harris , AIO v3 , Chapter-8 : Cryptography , Page : 638

Section: Analysis and Monitoring
Explanation/Reference:
Several analysis methods can be employed by an IDS, each with its own strengths and weaknesses, and their applicability to any given situation should be carefully considered.
There are two basic IDS analysis methods:
1. Pattern Matching (also called signature analysis), and
2. Anomaly detection
PATTERN MATCHING
Some of the first IDS products used signature analysis as their detection method and simply looked for known characteristics of an attack (such as specific packet sequences or text in the data stream) to produce an alert if that pattern was detected. If a new or different attack vector is used, it will not match a known signature and, thus, slip past the IDS.
ANOMALY DETECTION
Alternately, anomaly detection uses behavioral characteristics of a system's operation or network traffic to draw conclusions on whether the traffic represents a risk to the network or host. Anomalies may include but are not limited to:
Multiple failed log-on attempts
Users logging in at strange hours
Unexplained changes to system clocks
Unusual error messages
Unexplained system shutdowns or restarts
Attempts to access restricted files
An anomaly-based IDS tends to produce more data because anything outside of the expected behavior is reported. Thus, they tend to report more false positives as expected behavior patterns change. An advantage to anomaly-based IDS is that, because they are based on behavior identification and not specific patterns of traffic, they are often able to detect new attacks that may be overlooked by a signature-based system. Often information from an anomaly-based IDS may be used to create a pattern for a signature-based IDS.
Host Based Intrusion Detection (HIDS)
HIDS is the implementation of IDS capabilities at the host level. Its most significant difference from NIDS is that related processes are limited to the boundaries of a single-host system. However, this presents advantages in effectively detecting objectionable activities because the IDS process is running directly on the host system, not just observing it from the network. This offers unfettered access to system logs, processes, system information, and device information, and virtually eliminates limits associated with encryption. The level of integration represented by HIDS increases the level of visibility and control at the disposal of the HIDS application.
Network Based Intrustion Detection (NIDS)
NIDS are usually incorporated into the network in a passive architecture, taking advantage of promiscuous mode access to the network. This means that it has visibility into every packet traversing the network segment.
This allows the system to inspect packets and monitor sessions without impacting the network or the systems and applications utilizing the network.
Below you have other ways that instrusion detection can be performed:
Stateful Matching Intrusion Detection
Stateful matching takes pattern matching to the next level. It scans for attack signatures in the context of a stream of traffic or overall system behavior rather than the individual packets or discrete system activities. For example, an attacker may use a tool that sends a volley of valid packets to a targeted system. Because all the packets are valid, pattern matching is nearly useless. However, the fact that a large volume of the packets was seen may, itself, represent a known or potential attack pattern. To evade attack, then, the attacker may send the packets from multiple locations with long wait periods between each transmission to either confuse the signature detection system or exhaust its session timing window. If the IDS service is tuned to record and analyze traffic over a long period of time it may detect such an attack. Because stateful matching also uses signatures, it too must be updated regularly and, thus, has some of the same limitations as pattern matching.
Statistical Anomaly-Based Intrusion Detection
The statistical anomaly-based IDS analyzes event data by comparing it to typical, known, or predicted traffic profiles in an effort to find potential security breaches. It attempts to identify suspicious behavior by analyzing event data and identifying patterns of entries that deviate from a predicted norm. This type of detection method can be very effective and, at a very high level, begins to take on characteristics seen in IPS by establishing an expected baseline of behavior and acting on divergence from that baseline. However, there are some potential issues that may surface with a statistical IDS. Tuning the IDS can be challenging and, if not performed regularly, the system will be prone to false positives. Also, the definition of normal traffic can be open to interpretation and does not preclude an attacker from using normal activities to penetrate systems. Additionally, in a large, complex, dynamic corporate environment, it can be difficult, if not impossible, to clearly define
"normal" traffic. The value of statistical analysis is that the system has the potential to detect previously unknown attacks. This is a huge departure from the limitation of matching previously known signatures.
Therefore, when combined with signature matching technology, the statistical anomaly-based IDS can be very effective.
Protocol Anomaly-Based Intrusion Detection
A protocol anomaly-based IDS identifies any unacceptable deviation from expected behavior based on known network protocols. For example, if the IDS is monitoring an HTTP session and the traffic contains attributes that deviate from established HTTP session protocol standards, the IDS may view that as a malicious attempt to manipulate the protocol, penetrate a firewall, or exploit a vulnerability. The value of this method is directly related to the use of well-known or well-defined protocols within an environment. If an organization primarily uses well-known protocols (such as HTTP, FTP, or telnet) this can be an effective method of performing intrusion detection. In the face of custom or nonstandard protocols, however, the system will have more difficulty or be completely unable to determine the proper packet format. Interestingly, this type of method is prone to the same challenges faced by signature-based IDSs. For example, specific protocol analysis modules may have to be added or customized to deal with unique or new protocols or unusual use of standard protocols. Nevertheless, having an IDS that is intimately aware of valid protocol use can be very powerful when an organization employs standard implementations of common protocols.
Traffic Anomaly-Based Intrusion
Detection A traffic anomaly-based IDS identifies any unacceptable deviation from expected behavior based on actual traffic structure. When a session is established between systems, there is typically an expected pattern and behavior to the traffic transmitted in that session. That traffic can be compared to expected traffic conduct based on the understandings of traditional system interaction for that type of connection. Like the other types of anomaly-based IDS, traffic anomaly-based IDS relies on the ability to establish "normal" patterns of traffic and expected modes of behavior in systems, networks, and applications. In a highly dynamic environment it may be difficult, if not impossible, to clearly define these parameters.
Reference(s) used for this question:
Hernandez CISSP, Steven (2012-12-21). Official (ISC)2 Guide to the CISSP CBK, Third Edition ((ISC)2 Press) (Kindle Locations 3664-3686). Auerbach Publications. Kindle Edition.
and
Hernandez CISSP, Steven (2012-12-21). Official (ISC)2 Guide to the CISSP CBK, Third Edition ((ISC)2 Press) (Kindle Locations 3711-3734). Auerbach Publications. Kindle Edition.
and
Hernandez CISSP, Steven (2012-12-21). Official (ISC)2 Guide to the CISSP CBK, Third Edition ((ISC)2 Press) (Kindle Locations 3694-3711). Auerbach Publications. Kindle Edition.