How to build an effective purple team playbook

Red and blue make purple

In a nutshell, purple teaming involves organizations combining their offensive red teams -- those charged with simulating the behavior of threat actors -- with their defensive blue teams -- those analysts and other defensive personnel associated with protecting the company's systems.

As an enterprise security tool, purple teams use the collective knowledge of both red and blue team members, building collaborative engagement between the two teams to proactively spot vulnerabilities and security gaps in systems and processes and to improve incident response and an organization's security posture on a continuous basis.

Enterprises in all vertical industries can benefit from purple team exercises, but organizations in highly targeted sectors -- among them healthcare, critical infrastructure and finance -- likely have the most to gain.

Though not every organization has the resources to support both red and blue teams in-house, it is possible to outsource certain elements, such as penetration testing.

Benefits and importance of purple team playbooks

To be effective, a purple team needs a framework and playbooks.

A security framework is a set of documented processes that defines policies and procedures to manage risk and mitigate vulnerabilities. In general, a purple team framework involves the following steps similar to those of the NIST incident response framework:

• Preparation.
• Detection and analysis.
• Containment.
• Eradication and recovery.
• Post-incident activity.

A security playbook is a structured set of actionable, step-by-step instructions that lays out the tools and processes for responding to specific security incidents. Purple team playbooks outline the steps both red and blue teams should take to simulate and defend against adversarial tactics, techniques and procedures. Security playbooks are meant to be repeatable and reusable, so teams don't have to start from scratch during each exercise or event. They also help get team members on the same page and familiar with the proper steps to respond to an incident.

Organizations can have multiple different playbooks, based on types of attacks, scenarios and processes. Purple team playbooks and exercises are only successful when there is strong collaboration across red and blue teams. Playbooks should make sure offensive and defensive teams are aligned to identify and correct any problem areas discovered.

Purple team playbooks should also incorporate components that track and assess the exercises the red and blue teams run, as well as pinpoint the outcomes and optimization efforts. Assessments should include an accurate accounting of when and where vulnerabilities are discovered, if a breach occurs, how that incident was managed and what was done to prevent similar events in the future.

Vulnerability identification, threat intelligence and incident response underpin purple team exercises. With the proper playbooks and ensuing exercises, purple teaming offers benefits that range from faster threat identification and remediation to ongoing skill building.

Continuous improvement is a primary objective of purple teaming. Don't conduct any exercise in isolation; rather, perform interim tests to ensure an optimal security profile. Tool integration and ongoing skills development are also critical.

Types of purple team playbooks

From an offensive perspective, purple teams should simulate a wide range of attack situations and scenarios, such as the following:

• Phishing.
• Lateral movement.
• Ransomware.
• Penetration testing.
• Security operations center optimization.
• Threat hunting.
• Incident response.

From a defensive perspective, teams should perform vulnerability scans at regular intervals, patching any systems that require them. Network monitoring and defensive measures, such as identity and access management, are also important tools to test. Teams should also conduct regular system and network security audits, and they should encrypt high-value or sensitive data and restrict access to that data.

Effective risk management prioritizes security actions according to an incident's potential negative impact and determines how vulnerable a system or device might be. Based on what purple team playbooks reveal, it might be necessary to reassess or update an organization's security policies and practices.

Amy Larsen DeCarlo has covered the IT industry for more than 30 years, as a journalist, editor and analyst. As a principal analyst at GlobalData, she covers managed security and cloud services.