Rolling out a CDN is the best control to mitigate the Layer 4 DDoS attacks against the company website. A CDN is a Content Delivery Network, which is a system of distributed servers that deliver web content to users based on their geographic location, the origin of the web page, and the content delivery server. A CDN can help protect against Layer 4 DDoS attacks, which are volumetric attacks that aim to exhaust the network bandwidth or resources of the target website by sending a large amount of traffic, such as SYN floods, UDP floods, or ICMP floods. A CDN can mitigate these attacks by distributing the traffic across multiple servers, caching the web content closer to the users, filtering out malicious or unwanted traffic, and providing scalability and redundancy for the website12. Reference: How to Stop a DDoS Attack: Mitigation Steps for Each OSI Layer, Application layer DDoS attack | Cloudflare

Time synchronization issues can cause severe problems with authentication and logging. If system clocks are not properly synchronized, it can lead to discrepancies in log timestamps, making it difficult to correlate events across different systems. Additionally, time-related discrepancies can affect authentication mechanisms that rely on time-based tokens, such as those used in multifactor authentication, leading to failures and security gaps.

Time synchronization is the process of ensuring that all systems in a network have the same accurate time, which is essential for correlating data points from different sources. If the system has an issue with time synchronization, the analyst may have difficulty matching events that occurred at the same time or in a specific order. Access rights, network segmentation, and invalid playbook are not directly related to the issue of correlating data points. Verified Reference: [CompTIA CySA+ CS0-002 Certification Study Guide], page 23

Reimaging the device is the most effective way to eliminate persistent malware because some sophisticated malware, such as rootkits and firmware-level threats, can survive traditional scans and removals.
If a system keeps getting reinfected after cleaning, it may indicate a deeply embedded persistent threat, possibly in:
The Master Boot Record (MBR) or EFI firmware.
A compromised system restore point.
A hidden backdoor left by the malware.
Why Not Other Options?
A (Update and scan in safe mode) → Might help, but if malware is persistent, it will likely return.
C (Upgrade OS) → Does not necessarily remove malware; some malware survives OS upgrades.
D (Secondary scanner) → Useful for detection but does not guarantee complete removal.
Best Practice:
Replace the hard drive to eliminate firmware-level infections.
Reimage the system from a known-good source.
Update the OS and security patches before reconnecting to the network.

The best recommendations to prevent an XSS vulnerability from being exploited are to implement a compensating control in the source code and to fix the vulnerability using a virtual patch at the WAF. A compensating control is a technique that mitigates the risk of a vulnerability by adding additional security measures, such as input validation, output encoding, or HTML sanitization. A virtual patch is a rule that blocks or modifies malicious requests or responses at the WAF level, without modifying the application code. These recommendations are effective, efficient, and less disruptive than the other options. Reference: CompTIA CySA+ Study Guide: Exam CS0-003, 3rd Edition, Chapter 4: Security Operations and Monitoring, page 156; Cross Site Scripting Prevention Cheat Sheet, Section: XSS Defense Philosophy.