An NGFW (Next-Generation Firewall) utilizing application inspection could have identified and blocked the unusual use of HTTP over port 53. Application inspection allows NGFWs to analyze traffic at the application layer, identifying and blocking suspicious or non-standard protocol usage, such as HTTP traffic on DNS port
53.
* NGFW utilizing application inspection: Inspects traffic at the application layer and can block non- standard protocol usage, such as HTTP over port 53.
* WAF utilizing SSL decryption: Focuses on protecting web applications and decrypting SSL traffic but may not detect the use of HTTP over port 53.
* UTM utilizing a threat feed: Provides comprehensive security but may not focus specifically on application layer inspection.
* SD-WAN utilizing IPSec: Enhances secure WAN connections but is not primarily designed to inspect and block specific application traffic.

Explanation
An insider threat is a type of attack that originates from someone who has legitimate access to an organization's network, systems, or data. In this case, the domain user who encrypted the files on the database server is an example of an insider threat, as they abused their access privileges to cause harm to the organization. Insider threats can be motivated by various factors, such as financial gain, revenge, espionage, or sabotage.
References: CompTIA Security+ Study Guide: Exam SY0-701, 9th Edition, Chapter 1: General Security Concepts, page 251. CompTIA Security+ Certification Kit: Exam SY0-701, 7th Edition, Chapter 1: General Security Concepts, page 252.

Web-based administration is a feature that allows users to configure and manage routers through a web browser interface. While this feature can provide convenience and ease of use, it can also pose a security risk, especially if the web interface is exposed to the internet or uses weak authentication or encryption methods. Web-based administration can be exploited by attackers to gain unauthorized access to the router's settings, firmware, or data, or to launch attacks such as cross-site scripting (XSS) or cross-site request forgery (CSRF). Therefore, disabling web-based administration is a good practice to harden the routers within the corporate network. Console access, routing protocols, and VLANs are other features that can be configured on routers, but they are not the most appropriate to disable for hardening purposes. Console access is a physical connection to the router that requires direct access to the device, which can be secured by locking the router in a cabinet or using a strong password. Routing protocols are essential for routers to exchange routing information and maintain network connectivity, and they can be secured by using authentication or encryption mechanisms. VLANs are logical segments of a network that can enhance network performance and security by isolating traffic and devices, and they can be secured by using VLAN access control lists (VACLs) or private VLANs (PVLANs). Reference: CCNA SEC: Router Hardening Your Router's Security Stinks: Here's How to Fix It

Data classification is the process of assigning labels or tags to data based on its sensitivity, value, and risk.
Data classification is the first step in a data loss prevention (DLP) solution, as it helps to identify what data needs to be protected and how. By applying classifications to the data, thesecurity administrator can define appropriate policies and rules for the DLP solution to prevent the exfiltration of sensitive customer data. References: CompTIA Security+ Study Guide: Exam SY0-701, 9th Edition, Chapter 8: Data Protection, page 323. CompTIA Security+ Practice Tests: Exam SY0-701, 3rd Edition, Chapter 8: Data Protection, page
327.