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The “five factors” used to secure systems.

Common patterns that security teams use to mitigate risk.

Ryan McGeehan
Nov 8, 2017 · 8 min read
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1. Response: We’ll be ready to respond to the threat.

Adopt an “assume breach” mentality. Instead of directly mitigating the risk, you’ll commit to building the tools and policies needed to react upon that event. You will assume the event will happen, and you are advocating the preparation for an inevitable response.

  • A law firm, or response team on retainer.
  • An incident response plan for that risk
  • A drill for what could be an imminent incident.
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2. Evidence: We can trace the threat‘s steps.

You will not allow a risk to occur in a way that avoids the production of evidence. The event will occur while also revealing a root cause for a post-mortem, which lets you learn from mistakes.

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3. Containment: The threat will have limited impact.

It may be impossible to prevent an event from occurring, but you can make guarantees that damage will be limited when it does.

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4. Prevention: The threat isn’t likely to occur.

The “Prevention” factor commits to reducing the likelihood of a risk. When completed, the possibility a threat would succeed is unlikely or not at all applicable. Or, at least not without being detected.

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5. Elimination: Mitigation through innovation.

There were days when someone said:

  • “I can hurt bacteria with this weird mold” (September 1928)
  • “I can pass an encrypted message without a shared secret.” (1970)

One through Five: Defense in depth comes from multiple factors.

Introduce as many of these factors as efficiently as possible. Build infrastructure to increase that efficiency to eliminate unknown or one-off risks.

  1. Evidence: Logs, customer communications in support channels, and required postmortem process when we are surprised with an attack that succeeds.
  2. Containment: Requiring a re-authentication challenge when a user is making account deletion actions, which assumes the presence of CSRF. An attack shouldn’t cause data loss under normal circumstances.
  3. Prevention: Training, static analysis, code reviews, and audits to prevent coworkers introducing CSRF under odd circumstances.
  4. Elimination: A framework that avoids CSRF altogether.


Any mitigation strategy will choose from these different factors. It’s never as easy as applying them all, except in the most exceptional risks with the most awareness and cooperation from a group of people who care. Even mature organizations vary in how cooperative they are towards certain risks, and falling back on multiple factors of mitigation can help you pursue a measured approach to the best solution.

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