A DDoS attack is a type of attack that floods a target with more traffic than it can handle. This can cause the target to become unavailable to legitimate users.
The DNS logs will show the IP addresses of the devices that were sending the traffic to the target.
This information can be used to identify the attackers.
The other logs may also be helpful in investigating a DDoS attack, but they are less likely to provide the same level of detail as the DNS logs.

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.