Multi-Factor Authentication Risk Reduction Calculator
Estimates the reduction in account compromise risk when implementing Multi-Factor Authentication (MFA), based on baseline breach probability, MFA effectiveness, and user adoption rate.
Formulas Used
1. Residual risk for MFA-protected accounts:
P_protected = P_base × (1 − E_mfa)
Where P_base = baseline annual compromise probability, E_mfa = MFA effectiveness (fraction).
2. Blended residual risk across all accounts:
P_residual = A × P_protected + (1 − A) × P_base
= P_base × (1 − A × E_mfa)
Where A = MFA adoption rate (fraction). Accounts without MFA retain the full baseline risk.
3. Absolute Risk Reduction (ARR):
ARR = P_base − P_residual = P_base × A × E_mfa
4. Relative Risk Reduction (RRR):
RRR = ARR / P_base = A × E_mfa
5. Expected compromised accounts:
Breaches_before = P_base × N Breaches_after = P_residual × N Accounts_saved = Breaches_before − Breaches_after
6. Annual cost savings:
Cost_saved = Accounts_saved × Cost_per_breach
Assumptions & References
- MFA effectiveness values are drawn from Microsoft Security research (2019): SMS-based MFA blocks ~96% of automated attacks; authenticator-app / hardware-key MFA blocks ~99.9% of attacks. (Alex Weinert, Microsoft, 2019)
- Google's 2019 study corroborates: on-device prompts block 99% of bulk phishing and 90% of targeted attacks.
- Baseline breach probability is organisation-specific; industry averages range from 1% (low-risk) to 20%+ (high-value targets). The Verizon DBIR reports credential theft in ~80% of hacking-related breaches.
- The blended risk model assumes MFA-protected and unprotected accounts are independent and that attackers do not preferentially target unprotected accounts (conservative estimate).
- Cost per compromised account includes incident response, user remediation, and productivity loss. IBM Cost of a Data Breach Report 2023 estimates ~$150–$200 per record; per-account costs vary widely.
- This calculator models annual risk and does not account for multi-year compounding or attacker adaptation over time.
- References: Microsoft Security Blog (2019); Google/NYU/UCSD study "Protecting accounts from credential stuffing" (2019); Verizon DBIR 2023; IBM Cost of a Data Breach Report 2023.