CompTIA Updated CAS-004 Exam Questions and Answers by aarya

SaaS, or software as a service, is the solution that can best fulfill the requirements of having the lowest RTO possible, the least shared responsibility possible, and patching as a responsibility of the CSP. SaaS is a cloud service model that provides users with access to software applications hosted and managed by the CSP over the internet. SaaS has the lowest RTO (recovery time objective), which is the maximum acceptable time for restoring a system or service after a disruption, because it does not require any installation, configuration, or maintenance by the users. SaaS also has the least shared responsibility possible because most of the security aspects are handled by the CSP, such as patching, updating, backup, encryption, authentication, etc.

References: [CompTIA CASP+ Study Guide, Second Edition, pages 403-404]

The company should use HMAC SHA256 as a cryptographic technique to ensure that packets received between two parties have not been tampered with and the connection remains private. HMAC stands for hash-based message authentication code, which is a method of generating a message authentication code using a cryptographic hash function and a secret key. HMAC can provide both integrity and authenticity of the packets, as well as resistance to replay attacks. SHA256 is a specific hash function that produces a 256-bit output. SHA256 is considered secure and widely used in various cryptographic applications. Verified References:

• https://www.ericsson.com/en/blog/2021/7/cryptography-and-privacy-protecting-private-data
• https://www.mdpi.com/journal/cryptography/special_issues/Preserve_Enhance_Privacy
• https://link.springer.com/article/10.1007/s11432-021-3393-x

Input validation is a technique that checks the user input for any errors, malicious data, or unexpected values before processing it by the application. Input validation can prevent many common web application attacks, such as:

• SQL injection, which exploits a vulnerability in the application’s database query to execute malicious SQL commands.
• Cross-site scripting (XSS), which injects malicious JavaScript code into the application’s web page to execute on the client-side browser.
• Directory traversal, which accesses files or directories outside of the intended scope by manipulating the file path.

In this case, the security engineer should recommend input validation as the best mitigation technique, because it would:

• Prevent the exfiltration of a company report by validating the file parameter in the URL and ensuring that it matches a predefined list of allowed files or formats.
• Enhance the security of the web application by filtering out any malicious or invalid input from users or attackers.
• Be more effective and efficient than other techniques, such as firewall, WAF (Web Application Firewall), or DLP (Data Loss Prevention), which may not be able to detect or block all types of web application attacks.

OPC (Open Platform Communications) and Modbus are two common protocols used for industrial control systems (ICS). OPC is a standard that allows different devices and applications to exchange data in a vendor-neutral way. Modbus is a serial communication protocol that enables devices to send and receive commands and data over a network. Modbus has two variants: Modbus TCP/IP, which uses TCP port 502 for communication, and Modbus RTU/ASCII, which uses serial ports.

To allow an OPC server to communicate with a Modbus server that is controlling electrical relays, the security engineer should recommend restricting inbound traffic so that only the OPC server is permitted to reach the Modbus server on port 502. This configuration would:

• Permit the OPC server to send commands and data to the Modbus server using Modbus TCP/IP protocol over port 502.
• Limit operational disruptions, by preventing unauthorized or malicious access to the Modbus server from other sources.
• Due to the limitations within the Modbus protocol, such as lack of encryption and authentication, restricting inbound traffic is a necessary security measure to protect the integrity and availability of the ICS.