Monday, April 28, 2014

CISA Exam Preparation (Question 1 ~ 10)

(1) An internet-based attack using password sniffing can:
A. enable one party to act as if they are another party.
B. cause modification to the contents of certain transactions.
C. be used to gain access to systems containing proprietary information.
D. result in major problems with billing systems and transaction processing agreements.

Explanation:
Password sniffing attacks can be used to gain access to systems on which proprietary information is stored. Spoofing attacks can be used to enable one party to act as if they are another party.
Data modification attacks can be used to modify the contents of certain transactions. Repudiation of transactions can cause major problems with billing systems and transaction processing agreements.

(2) Which of the following controls would be the MOST comprehensive in a remote access network with multiple and diverse subsystems?
A. Proxy server
B. Firewall installation
C. Network administrator
D. Password implementation and administration

Explanation:
The most comprehensive control in this situation is password implementation and administration. While firewall installations are the primary line of defense, they cannot protect all access and, therefore, an element of risk remains. A proxy server is a type of firewall installation; thus, the same rules apply. The network administrator may serve as a control, but typically this would not be comprehensive enough to serve on multiple and diverse systems.

(3) During an audit of an enterprise that is dedicated to e-commerce, the IS manager states that digital signatures are used when receiving communications from customers. To substantiate this, an IS auditor must prove that which of the following is used?
A. A biometric, digitalized and encrypted parameter with the customer’s public key
B. A hash of the data that is transmitted and encrypted with the customer’s private key
C. A hash of the data that is transmitted and encrypted with the customer’s public key
D. The customer’s scanned signature encrypted with the customer’s public key

Explanation:
The calculation of a hash, or digest, of the data that are transmitted and its encryption require the public key of the client (receiver) and is called a signature of the message, or digital signature. The receiver performs the same process and then compares the received hash, once it has been decrypted with their private key, to the hash that is calculated with the received datA . If they are the same, the conclusion would be that there is integrity in the data that have arrived and the origin is authenticated. The concept of encrypting the hash with the private key of the originator provides non repudiation, as it can only be decrypted with their public key and, as the CD suggests, the private key would not be known to the recipient. Simply put, in a key-pair situation, anything that can be decrypted by a sender’s public key must have been encrypted with their private key, so they must have been the sender, i.e., non repudiation. Choice C is incorrect because, if this were the case, the hash could not be decrypted by the recipient, so the benefit of non repudiation would be lost and there could be no verification that the message had not been intercepted and amended. A digital signature is created by encrypting with a private key. A person creating the signature uses their own private key, otherwise everyone would be able to create a signature with any public key. Therefore, the signature of the client is created with the client’s private key, and this can be verified-by
.

(4) When planning an audit of a network setup, an IS auditor should give highest priority to obtaining which of the following network documentation?
A. Wiring and schematic diagram
B. Users’ lists and responsibilities
C. Application lists and their details
D. Backup and recovery procedures

Explanation:
The wiring and schematic diagram of the network is necessary to carry out a network audit. A network audit may not be feasible if a network wiring and schematic diagram is not available. All other documents are important but not necessary.

(5) Which of the following encrypt/decrypt steps provides the GREATEST assurance of achieving confidentiality, message integrity and nonrepudiation by either sender or recipient?
A. The recipient uses their private key to decrypt the secret key.
B. The encryptedprehash code and the message are encrypted using a secret key.
C. The encryptedprehash code is derived mathematically from the message to be sent.
D. The recipient uses the sender’s public key, verified with a certificate authority, to decrypt theprehash code.

Explanation:
Most encrypted transactions use a combination of private keys, public keys, secret keys, hash functions and digital certificates to achieve confidentiality, message integrity and nonrepudiation by either sender or recipient. The recipient uses the sender’s public key to decrypt the prehash code into a posthash code, which when equaling the prehash code, verifies the identity of the sender and that the message has not been changed in route; this would provide the greatest assurance. Each sender and recipient has a private key known only to themselves and a public key, which can be known by anyone. Each encryption/decryption process requires at least one public key and one private key, and both must be from the same party. A single, secret key is used to encrypt the message, because secret key encryption requires less processing power than using public and private keys. A digital certificate, signed by a certificate authority, validates senders’ and recipients’ public keys.

(6) Use of asymmetric encryption in an internet e-commerce site, where there is one private key for the hosting server and the public key is widely distributed to the customers, is MOST likely to provide comfort to the:

A. customer over the authenticity of the hosting organization.
B. hosting organization over the authenticity of the customer.
C. customer over the confidentiality of messages from the hosting organization.
D. hosting organization over the confidentiality of messages passed to the customer.

Explanation:
Any false site will not be able to encrypt using the private key of the real site, so the customer would not be able to decrypt the message using the public key. Many customers have access to the same public key so the host cannot use this mechanism to ensure the authenticity of the customer. The customer cannot be assured of the confidentiality of messages from the host as many people have access to the public key and can decrypt the messages from the host. The host cannot be assured of the confidentiality of messages sent out, as many people have access to the public key and can decrypt it.
(7) E-mail message authenticity and confidentiality is BEST achieved by signing the message using the:

A. sender’s private key and encrypting the message using the receiver’s public key.
B. sender’s public key and encrypting the message using the receiver’s private key.
C. receiver’s private key and encrypting the message using the sender’s public key.
D. receiver’s public key and encrypting the message using the sender’s private key.

Explanation:
By signing the message with the sender’s private key, the receiver can verify its authenticity using the sender’s public key. By encrypting the message with the receiver’s public key, only the receiver can decrypt the message using their own private key. The receiver’s private key is confidential and, therefore, unknown to the sender. Messages encrypted using the sender’s private key can be read by anyone with the sender’s public key.
(8) An organization is considering connecting a critical PC-based system to the Internet. Which of the following would provide the BEST protection against hacking?
A. An application-level gateway
B. A remote access server
C. A proxy server
D. Port scanning

Explanation:
An application-level gateway is the best way to protect against hacking because it can define with detail rules that describe the type of user or connection that is or is not permitted, it analyzes in detail each package, not only in layers one through four of the OSI model but also layers five through seven, which means that it reviews the commands of each higher-level protocol (HTTP, FTP, SNMP, etc.). For a remote access server, there is a device (server) that asks for a username and password before entering the network. This is good when accessing private networks, but it can be mapped or scanned from the Internet creating security exposure. Proxy servers can provide protection based on the IP address and ports. However, an individual is needed who really knows how to do this, and applications can use different ports for the different sections of the program. Port scanning works when there is a very specific task to complete, but not when trying to control what comes from the Internet, or when all the ports available need to be controlled. For example, the port for Ping (echo request) could be blocked and the IP addresses would be available for the application and browsing, but would not respond to Ping .
(9) Applying a digital signature to data traveling in a network provides:
A. confidentiality and integrity.
B. security andnonrepudiation.
C. integrity andnonrepudiation.
D. confidentiality andnonrepudiation.

Explanation:
The process of applying a mathematical algorithm to the data that travel in the network and placing the results of this operation with the hash data is used for controlling data integrity, since any unauthorized modification to this data would result in a different hash. The application of a digital signature would accomplish the non repudiation of the delivery of the message. The term security is a broad concept and not a specific one. In addition to a hash and a digital signature, confidentiality is applied when an encryption process exists.
(10) Which of the following would an IS auditor consider a weakness when performing an audit of an organization that uses a public key infrastructure with digital certificates for its business-to- consumer transactions via the internet?
A. Customers are widely dispersed geographically, but the certificate authorities are not.
B. Customers can make their transactions from any computer or mobile device.
C. The certificate authority has several data processingsubcenters to administer certificates.
D. The organization is the owner of the certificate authority.


Explanation:
If the certificate authority belongs to the same organization, this would generate a conflict of interest. That is, if a customer wanted to repudiate a transaction, they could allege that because of the shared interests, an unlawful agreement exists between the parties generating the certificates, if a customer wanted to repudiate a transaction, they could argue that there exists a bribery between the parties to generate the certificates, as shared interests exist. The other options are not weaknesses.

- Muhammad Idham Azhari

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