How Walmart Uses a Purple Team to Improve Cyber-Resilience

RSA Conference 2019: Applying a collaborative, yet adversarial model has worked out well for Walmart as it works to reduce risk and improve cyber-security.

Walmart Purple Team

SAN FRANCISCO — Few if any, organizations on the planet operate at the size and scale of Walmart. Scale isn't just about normal retail operations either; it also comes in play with how the organization handles its own security resiliency testing.

In a session at the RSA Conference here, Jason O'Dell, director of incident response and hunt at Walmart, explained how the world's largest retailer uses an innovative approach known as purple teaming at scale to improve security and reduce risk.

A Red Team is well-known in cyber-security as a group within an organization that will conduct offensive operations to help identify areas of weakness. A Blue Team, on the other hand, is the group within an organization that is tasked with defending against adversaries and Red Team activities. The Purple Team idea brings Red and Blue teams together.

"Purple is the symbiotic relationship between Red and Blue in a way that improves the security of the organization, constantly improving the skill and processes of both teams," O'Dell said.

O'Dell said that Walmart began on its Purple Team journey in 2016, and the effort didn't start well at all for a number of reasons. The nature of Red and Blue teaming is adversarial, and that created conflict. If the Red Team wins, it means there is a breach, and if the Blue Team wins it means an attack was contained.  O'Dell emphasized, however, that what Walmart learned is that while winning is interesting, that's not what matters in a Purple Team exercise.

"It's not about winning or losing; it's about learning," he said. "Winning is the objective of the game, but it's not the objective of playing the game. The objective of the game is for the organization to get better."

How Purple Teaming Should Work

A key thing that Walmart has learned is that the Red and Blue teams need to work in the best interests of the organization. O'Dell said that both teams should act as advocates for the other with upper management to share the successes of each team.

For the actual threat exercises, O'Dell said there several steps that all organizations should take:

  • Rules of engagement.  Make sure each side understands what is or isn't in scope.
  • Have a central repository. Track all the findings of the exercise to improve collaboration and metrics tracking.
  • Use a common taxonomy. Having a common framework and methodology to understand attack is also important. O'Dell said that Walmart now makes uses of the MITRE ATT&CK Framework, which outlines and categorized different attack vectors.
  • Collaborate on the final report. Rather than each team writing its own report, Red and Blue should work together on findings report that is presented and shared with management.

Having a Purple Team isn't right for every organization, but for those where they have the resources, O'Dell said that an initial first step is to do a tabletop exercise. A tabletop is essentially a discussion and collaboration about how one side would do one action and then how the other side will respond.

Following the tabletop, the next step is to have an active threat simulation where attacks and defences can be simulated. Finally, after conducting successful tabletops and threat simulations, O'Dell said that the organization can then conduct a full adversarial engagement. O'Dell said the adversarial engagement should have comprehensive rules of engagement, real-time communication during the campaign and initial metrics to track success.

Sean Michael Kerner is a senior editor at eWEEK and Follow him on Twitter @TechJournalist.

Sean Michael Kerner

Sean Michael Kerner

Sean Michael Kerner is an Internet consultant, strategist, and contributor to several leading IT business web sites.