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Return on Security Investment (ROSI)

A metric that quantifies the financial benefit of security investments relative to their cost.

Risk & ResilienceAlso called: "rosi", "security roi"

ROSI helps justify security spending by demonstrating risk reduction value.

Calculation

ROSI = (Risk Mitigated - Security Cost) / Security Cost

Components

  • Risk before: Annual Loss Expectancy (ALE) = Impact × Probability.
  • Risk after: Reduced ALE with controls in place.
  • Risk mitigated: Difference between before/after.
  • Security cost: Total cost of implementation and operation.

Example

  • Annual breach risk: $5M.
  • Control cost: $500K.
  • Risk reduction: 60% = $3M mitigated.
  • ROSI = ($3M - $500K) / $500K = 500%.

Challenges

  • Difficult to quantify intangible benefits.
  • Probability estimates are uncertain.
  • Compliance requirements may override ROI.
  • Prevention value vs detection/response value.