Which of the following is NOT true about IPSec Tunnel mode?
Correct Answer: B
IPSec can be run in either tunnel mode or transport mode. Each of these modes has its own particular uses and care should be taken to ensure that the correct one is selected for the solution: Tunnel mode is most commonly used between gateways, or at an end-station to a gateway, the gateway acting as a proxy for the hosts behind it. Transport mode is used between end-stations or between an end-station and a gateway, if the gateway is being treated as a host-for example, an encrypted Telnet session from a workstation to a router, in which the router is the actual destination. As Figure 1 shows, basically transport mode should be used for end-to-end sessions and tunnel mode should be used for everything else. (Refer to the figure for the following discussion.) Figure 1 Tunnel and transport modes in IPSec. Figure 1 displays some examples of when to use tunnel versus transport mode: Tunnel mode is most commonly used to encrypt traffic between secure IPSec gateways, such as between the Cisco router and PIX Firewall (as shown in example A in Figure 1). The IPSec gateways proxy IPSec for the devices behind them, such as Alice's PC and the HR servers in Figure 1. In example A, Alice connects to the HR servers securely through the IPSec tunnel set up between the gateways. Tunnel mode is also used to connect an end-station running IPSec software, such as the Cisco Secure VPN Client, to an IPSec gateway, as shown in example B. In example C, tunnel mode is used to set up an IPSec tunnel between the Cisco router and a server running IPSec software. Note that Cisco IOS software and the PIX Firewall sets tunnel mode as the default IPSec mode. Transport mode is used between end-stations supporting IPSec, or between an end-station and a gateway, if the gateway is being treated as a host. In example D, transport mode is used to set up an encrypted Telnet session from Alice's PC running Cisco Secure VPN Client software to terminate at the PIX Firewall, enabling Alice to remotely configure the PIX Firewall securely. AH Tunnel Versus Transport Mode Figure 2 shows the differences that the IPSec mode makes to AH. In transport mode, AH services protect the external IP header along with the data payload. AH services protect all the fields in the header that don't change in transport. The header goes after the IP header and before the ESP header, if present, and other higher-layer protocols. In tunnel mode, the entire original header is authenticated, a new IP header is built, and the new IP header is protected in the same way as the IP header in transport mode. Figure 2 AH tunnel versus transport mode. AH is incompatible with Network Address Translation (NAT) because NAT changes the source IP address, which breaks the AH header and causes the packets to be rejected by the IPSec peer. ESP Tunnel Versus Transport Mode Figure 3 shows the differences that the IPSec mode makes to ESP. In transport mode, the IP payload is encrypted and the original headers are left intact. The ESP header is inserted after the IP header and before the upper-layer protocol header. The upper-layer protocols are encrypted and authenticated along with the ESP header. ESP doesn't authenticate the IP header itself. NOTE Higher-layer information is not available because it's part of the encrypted payload. When ESP is used in tunnel mode, the original IP header is well protected because the entire original IP datagram is encrypted. With an ESP authentication mechanism, the original IP datagram and the ESP header are included; however, the new IP header is not included in the authentication. When both authentication and encryption are selected, encryption is performed first, before authentication. One reason for this order of processing is that it facilitates rapid detection and rejection of replayed or bogus packets by the receiving node. Prior to decrypting the packet, the receiver can detect the problem and potentially reduce the impact of denial-of-service attacks. Figure 3 ESP tunnel versus transport mode. ESP can also provide packet authentication with an optional field for authentication. Cisco IOS software and the PIX Firewall refer to this service as ESP hashed message authentication code (HMAC). Authentication is calculated after the encryption is done. The current IPSec standard specifies SHA-1 and MD5 as the mandatory HMAC algorithms. The main difference between the authentication provided by ESP and AH is the extent of the coverage. Specifically, ESP doesn't protect any IP header fields unless those fields are encapsulated by ESP (tunnel mode). Figure 4 illustrates the fields protected by ESP HMAC. Figure 4 ESP encryption with a keyed HMAC. IPSec Transforms An IPSec transform specifies a single IPSec security protocol (either AH or ESP) with its corresponding security algorithms and mode. Example transforms include the following: The AH protocol with the HMAC with MD5 authentication algorithm in tunnel mode is used for authentication. The ESP protocol with the triple DES (3DES) encryption algorithm in transport mode is used for confidentiality of data. The ESP protocol with the 56-bit DES encryption algorithm and the HMAC with SHA-1 authentication algorithm in tunnel mode is used for authentication and confidentiality. Transform Sets A transform set is a combination of individual IPSec transforms designed to enact a specific security policy for traffic. During the ISAKMP IPSec security association negotiation that occurs in IKE phase 2 quick mode, the peers agree to use a particular transform set for protecting a particular data flow. Transform sets combine the following IPSec factors: Mechanism for payload authentication-AH transform Mechanism for payload encryption-ESP transform IPSec mode (transport versus tunnel) Transform sets equal a combination of an AH transform, plus an ESP transform, plus the IPSec mode (either tunnel or transport mode). This brings us to the end of the second part of this five-part series of articles covering IPSec. Be sure to catch the next installment. Cisco Press at: http://www.ciscopress.com/articles/printerfriendly.asp?p=25477 and Source: TIPTON, Harold F. & KRAUSE, MICKI, Information Security Management Handbook, 4th Edition, Volume 2, 2001, CRC Press, NY, Pages 166-167.
Question 422
In addition to the accuracy of the biometric systems, there are other factors that must also be considered:
Correct Answer: C
In addition to the accuracy of the biometric systems, there are OTHER factors that must also be considered. These factors include the enrollment time, the throughput rate, and acceptability. -Ronald Krutz The CISSP PREP Guide (gold edition) pg 51
Question 423
What is the three way handshake sequence used to initiate TCP connections?
Correct Answer: B
The TCP three way handshake: 1 . First, the client sends a SYN segment. This is a request to the server to synchronize the sequence numbers. It specifies its initial sequence number (ISN), which is incremented by 1 , and that is sent to the server. To initialize a connection, the client and server must synchronize each other's sequence numbers. 2 . Second, the server sends an ACK and a SYN in order to acknowledge the request of the client for synchronization. At the same time, the server is also sending its request to the client for synchronization of its sequence numbers. There is one major difference in this transmission from the first one. The server transmits an acknowledgement number to the client. The acknowledgement is just proof to the client that the ACK is specific to the SYN the client initiated. The process of acknowledging the client's request allows the server to increment the client's sequence number by one and uses it as its acknowledgement number. 3. Third, the client sends an ACK in order to acknowledge the request from the server for synchronization. The client uses the same algorithm the server implemented in providing an acknowledgement number. The client's acknowledgment of the server's request for synchronization completes the process of establishing a reliable connection. The following answers are incorrect: All of the other choices were incorrect answers The following reference(s) were/was used to create this question: Hernandez CISSP, Steven (2012-12-21). Official (ISC)2 Guide to the CISSP CBK, Third Edition ((ISC)2 Press) (Kindle Locations 5560-5573). Auerbach Publications. Kindle Edition.
Question 424
Management can expect penetration tests to provide all of the following EXCEPT
Correct Answer: C
Not B: It is not the objective of the pen tester to supply a method on how to correct the flaws. In fact management may decide to accept the risk and not repair the flaw. They may be able to demonstrate the effects of a flaw - especially if they manage to clobber a system! Penetration testing is a set of procedures designed to test and possibly bypass security controls of a system. Its goal is to measure an organization's resistance to an attack and to uncover any weaknesses within the environment...The result of a penetration test is a report given to management describing the list of vulnerabilities that were identified and the severity of those vulnerabilities. From here, it is up to management to determine how the vulnerabilities are dealt with and what countermeasures are implemented. - Shon Harris All-in-one CISSP Certification Guide pg 837-839
Question 425
What is the second phase of Public Key Infrastructure (PKI) key/certificate life-cycle management?
Correct Answer: D
Section: Security Architecture and Engineering Explanation/Reference:
