Which of the following is NOT one of the five phases of an incident response playbook?

The five phases of an incident response playbook are typically recognized as preparation, detection and analysis, containment, eradication, and recovery. The rationale behind these specific phases is rooted in the methodology for effectively managing and mitigating cybersecurity incidents.

Preparation involves establishing and training the incident response team, developing an incident response plan, and ensuring that the organization has the necessary tools and resources. Detection focuses on identifying potential security incidents and analyzing them to determine their severity and impact. Recovery is the phase where the organization restores services and operations after an incident while also implementing improvements to prevent future occurrences.

Validation, while it may play a role in specific contexts of incident response (such as validating the effectiveness of new controls post-incident), is not typically classified as one of the core phases in the standard playbook framework. This distinction underscores why it is the correct answer to the question.