Input validation is a security technique that checks the user input for any malicious or unexpected data before processing it by the application. Input validation can prevent various types of attacks, such as injection, cross-site scripting, buffer overflow, and command execution, that exploit the vulnerabilities in the application code. Input validation can be performed on both the client-side and the server-side, using methods such as whitelisting, blacklisting, filtering, sanitizing, escaping, and encoding. By including regular expressions in the source code to remove special characters from the variables set by the forms in the web application, the organization adopted input validation as a security technique. Regular expressions are patterns that match a specific set of characters or strings, and can be used to filter out any unwanted or harmful input. Special characters, such as $, |, ;, &, `, and ?, can be used by attackers to inject commands or scripts into the application, and cause damage or data theft. By removing these characters from the input, the organization can reduce the risk of such attacks.
Identify embedded keys, code debugging, and static code analysis are not the security techniques that the organization adopted by making this addition to the policy. Identify embedded keys is a process of finding and removing any hard-coded keys or credentials from the source code, as these can pose a security risk if exposed or compromised. Code debugging is a process of finding and fixing any errors or bugs in the source code, which can affect the functionality or performance of the application. Static code analysis is a process of analyzing the source code without executing it, to identify any vulnerabilities, flaws, or coding standards violations. These techniques are not related to the use of regular expressions to remove special characters from the input.
Reference = CompTIA Security+ SY0-701 Certification Study Guide, page 375-376; Professor Messer's CompTIA SY0-701 Security+ Training Course, video 4.1 - Vulnerability Scanning, 8:00 - 9:08; Application Security - SY0-601 CompTIA Security+ : 3.2, 0:00 - 2:00.

The scenario indicates that a user downloaded an unofficial patch, applied it, and afterward system files changed-detected by FIM. This strongly suggests the presence of a rootkit, which is designed to deeply embed itself into the operating system, altering core system files, modifying kernels, and hiding its presence.
Rootkits commonly replace or modify OS-level files, which results in changed file hashes-exactly what FIM is detecting. Rootkits often gain privileged, persistent control and are frequently disguised as legitimate updates or patches.
A logic bomb (A) is triggered by an event but does not typically modify OS files. A keylogger (B) captures keystrokes but doesn't modify system files broadly. Ransomware (C) encrypts files, not silently alters system components.
Thus, the best match is D: Rootkit.

Deploying a Security Information and Event Management (SIEM) solution allows for efficient log aggregation, correlation, and analysis across an organization's infrastructure, providing real-time security insights.Reference: Security+ SY0-701 Course Content, Security+ SY0-601 Book.

User Behavior Analytics (UBA)is specifically designed to detectanomalous or suspicious behaviorsby users that may indicate insider threats. UBA toolsestablish a baseline of normalbehaviorfor users and alert security teams when deviations occur (e.g., accessing sensitive files at odd hours, downloading large volumes of data, etc.).
Malicious insiders often bypass perimeter defenses like firewalls or IDS/IPS systems because they are legitimate users. UBA offersvisibility into internal behavior patterns, which is essential for detecting these threats.