What CS0-003 Questions and Answers feature?

The correct answer is A. Configure the server to prefer TLS 1.3 and B. Remove cipher suites that use CBC.

A padding oracle attack is a type of attack that exploits the padding validation of a cryptographic message to decrypt the ciphertext without knowing the key. A padding oracle is a system that responds to queries about whether a message has a valid padding or not, such as a web server that returns different error messages for invalid padding or invalid MAC. A padding oracle attack can be applied to the CBC mode of operation, where the attacker can manipulate the ciphertext blocks and use the oracle’s responses to recover the plaintext12.

To remediate this issue, the organization should make the following configuration changes:

Configure the server to prefer TLS 1.3. TLS 1.3 is the latest version of the Transport Layer Security protocol, which provides secure communication between clients and servers. TLS 1.3 has several security improvements over previous versions, such as:

It deprecates weak and obsolete cryptographic algorithms, such as RC4, MD5, SHA-1, DES, 3DES, and CBC mode.

It supports only strong and modern cryptographic algorithms, such as AES-GCM, ChaCha20-Poly1305, and SHA-256/384.

It reduces the number of round trips required for the handshake protocol, which improves performance and latency.

It encrypts more parts of the handshake protocol, which enhances privacy and confidentiality.

It introduces a zero round-trip time (0-RTT) mode, which allows resuming previous sessions without additional round trips.

It supports forward secrecy by default, which means that compromising the long-term keys does not affect the security of past sessions3456.

Remove cipher suites that use CBC. Cipher suites are combinations of cryptographic algorithms that specify how TLS connections are secured. Cipher suites that use CBC mode are vulnerable to padding oracle attacks, as well as other attacks such as BEAST and Lucky 13. Therefore, they should be removed from the server’s configuration and replaced with cipher suites that use more secure modes of operation, such as GCM or CCM78.

The other options are not effective or necessary to remediate this issue.

Option C is not effective because configuring the server to prefer ephemeral modes for key exchange does not prevent padding oracle attacks. Ephemeral modes for key exchange are methods that generate temporary and random keys for each session, such as Diffie-Hellman or Elliptic Curve Diffie-Hellman. Ephemeral modes provide forward secrecy, which means that compromising the long-term keys does not affect the security of past sessions. However, ephemeral modes do not protect against padding oracle attacks, which exploit the padding validation of the ciphertext rather than the key exchange9.

Option D is not necessary because requiring client browsers to present a user certificate for mutual authentication does not prevent padding oracle attacks. Mutual authentication is a process that verifies the identity of both parties in a communication, such as using certificates or passwords. Mutual authentication enhances security by preventing impersonation or spoofing attacks. However, mutual authentication does not protect against padding oracle attacks, which exploit the padding validation of the ciphertext rather than the authentication.

Option E is not necessary because configuring the server to require HSTS does not prevent padding oracle attacks. HSTS stands for HTTP Strict Transport Security and it is a mechanism that forces browsers to use HTTPS connections instead of HTTP connections when communicating with a web server. HSTS enhances security by preventing downgrade or man-in-the-middle attacks that try to intercept or modify HTTP traffic. However, HSTS does not protect against padding oracle attacks, which exploit the padding validation of HTTPS traffic rather than the protocol.

Option F is not effective because removing cipher suites that use GCM does not prevent padding oracle attacks. GCM stands for Galois/Counter Mode and it is a mode of operation that provides both encryption and authentication for block ciphers, such as AES. GCM is more secure and efficient thanCBC mode, as it prevents various types of attacks, such as padding oracle, BEAST, Lucky 13, and IV reuse attacks. Therefore, removing cipher suites that use GCM would reduce security rather than enhance it .

Comprehensive Detailed Explanation:The most effective and economical way to ensure the security of an automated information system is to design it with security in mind from the outset. This is often referred to as "security by design." Here’s a breakdown of each option and why option A is correct:

A. Originally designed to provide necessary security

Explanation: Systems designed with security from the beginning integrate secure practices and considerations during the development process. This approach mitigates the need for costly and complex retroactive security implementations, which are common in systems where security was an afterthought.

Cost Efficiency: Security implementations at the design stage can be embedded into the system architecture, reducing the costs associated with later modifications.

Effectiveness: Security-by-design approaches often result in robust systems that are more resilient to vulnerabilities because they address security concerns at each development phase.

B. Subjected to intense security testing

While rigorous security testing (such as penetration testing and vulnerability assessments) is essential, it is reactive. Security testing is more effective when applied to systems already designed with foundational security principles, ensuring that tests identify potential flaws in an inherently secure system.

C. Customized to meet specific security threats

Customizing security to meet specific threats addresses unique risks, but such a targeted approach may miss new or emerging threats not initially considered. It also risks neglecting fundamental security practices that apply universally, leading to potential vulnerabilities.

D. Optimized prior to the addition of security

Optimizing a system before adding security features may enhance performance but does not guarantee security. Security cannot be effectively added onto a system as an afterthought without incurring additional costs or creating potential weaknesses.

Mitigate is the best term to describe the risk management principle that the company is exercising, as it means to reduce the likelihood or impact of a risk. By implementing a patch management program to remediate vulnerabilities, the company is mitigating the threat of cyberattacks that could exploit those vulnerabilities and compromise the security or functionality of the systems. The other terms are not as accurate as mitigate, as they describe different risk management principles. Transfer means to shift theresponsibility or burden of a risk to another party, such as an insurer or a contractor. Accept means to acknowledge the existence of a risk and decide not to take any action to reduce it, usually because the risk is low or the cost of mitigation is too high. Avoid means to eliminate the possibility of a risk by changing the plans or activities that could cause it, such as cancelling a project or discontinuing a service.