Why do multi-factor authentication and biometrics still leave gaps in account security?

Why This Matters for Security Teams

MFA and biometrics improve account security, but they do not close every path an attacker can use. Modern compromises often target enrollment, recovery, session hijacking, help desk workflows, or the device that holds the second factor rather than the password itself. That is why a control can be technically “enabled” while the account remains practically recoverable by an adversary. Guidance in NIST SP 800-53 Rev 5 Security and Privacy Controls treats authentication as only one layer in a broader access-control and assurance model, not a final guarantee of identity legitimacy.

For NHI Management Group, the same pattern appears across both human and non-human access: the weakest point is often not the secret itself, but the process around it. In the wild, attackers frequently work around strong factors by abusing recovery routes, consent grants, or exposed sessions rather than defeating the factor directly. In practice, many security teams discover that MFA failed only after an account takeover has already moved into email, SaaS, or cloud control planes, rather than through an intentional assurance review.

How It Works in Practice

The gap exists because authentication strength and account lifecycle integrity are not the same thing. MFA proves that a user presented an additional factor at one moment in time. Biometrics can improve convenience and raise the bar for casual abuse, but they still depend on the enrolled device, the recovery path, and the trust placed in the identity provider. If any of those pieces are weak, the overall account can still be compromised.

Security teams should evaluate the full access journey, not just the login prompt. That means reviewing:

• Enrollment controls, including who can bind a new device or biometric template
• Recovery paths, especially help desk resets, backup codes, and identity proofing steps
• Session protection, including token theft, long-lived sessions, and device trust
• Privilege escalation after login, such as admin consent, mailbox forwarding, or API token creation
• Monitoring for anomalous access that bypasses the expected MFA flow

This is especially important for accounts that can create secrets, approve workflows, or manage other identities. The Ultimate Guide to NHIs shows how broader identity risk is often driven by privilege, visibility, and weak lifecycle controls, not just initial authentication. It also notes that 97% of NHIs carry excessive privileges, which is a strong reminder that once an account is inside, over-broad access can magnify a small authentication failure into a major incident.

For high-value accounts, current best practice is to combine phishing-resistant MFA, tightly controlled recovery, device posture checks, and least privilege. Biometrics can reduce credential replay, but they should be treated as an assurance input, not a standalone trust decision. In practice, these controls tend to break down in organizations with outsourced service desks and inconsistent identity proofing because attackers target the override process, not the biometric factor itself.

Common Variations and Edge Cases

Tighter authentication often increases user friction and support overhead, requiring organisations to balance stronger assurance against operational usability. That tradeoff is real, especially in environments with contractors, shared workstations, field devices, or legacy apps that cannot support modern authentication flows. Current guidance suggests that the right answer is usually not “more MFA everywhere,” but a better fit between factor type, account risk, and recovery governance.

Some edge cases deserve special attention. Biometric systems can be vulnerable to spoofing, sensor failure, or fallback paths that quietly weaken the original design. MFA can also be bypassed through push fatigue, SIM swap attacks, token theft, or session reuse if the application treats the second factor as a one-time event rather than part of continuous assurance. For regulated environments, ISO/IEC 27001:2022 Information Security Management and eIDAS 2.0 — EU Digital Identity Framework both reinforce that identity assurance depends on governance, proofing, and lifecycle controls, not a single technical factor.

The practical rule is simple: if an attacker can re-enroll the account, reset the factor, steal the session, or approve their own recovery, MFA and biometrics have not actually closed the door. That is why mature programmes treat authentication as one control in a larger identity security architecture, with continuous review of recovery, privilege, and session integrity.

Related resources from NHI Mgmt Group

• When does multi-factor authentication still leave organisations exposed to account takeover?
• How should security teams implement iris biometrics in multi-factor authentication without over-relying on them?
• What breaks when multi-factor authentication is still built around passwords and basic biometrics?
• When do passkeys improve security but still leave governance gaps?