Why MFA Isn’t a Silver Bullet (and What Completes the Picture)

Multi-factor authentication (MFA) is one of the best things you can implement for identity security.

But it’s not enough.

It’s often deployed as the “job done” checkbox in security roadmaps—when in reality, it should be the start of a broader strategy.

Yes, MFA blocks the vast majority of password-based attacks.

But here’s the reality: attackers evolve. And MFA, by itself, can be bypassed.

Where MFA Falls Short

It’s important to understand that MFA only protects one part of the process: authentication.

Once a user is authenticated—even if it’s a real user, logging in from their device—security needs to continue.

Here’s where MFA breaks down:

1. MFA Fatigue Attacks

Attackers use bots or scripts to flood users with MFA prompts. The user gets annoyed and hits “Approve” just to stop the noise.

It’s not a technical flaw. It’s behavioural.

2. Phishing MFA Codes

Modern phishing kits now capture not just usernames and passwords, but also OTPs and push approvals.

Some even spoof legitimate login portals to grab the second factor in real time.

3. Session Hijacking

Once MFA is completed, a session token is created. If that token is compromised (e.g., through malware or browser attacks), attackers can hijack the session without triggering another MFA check.

This means “getting past MFA” doesn’t always require breaching MFA itself.

4. MFA Gaps

Not all services support MFA. Legacy systems, third-party apps, or BYOD scenarios often introduce blind spots—places where credentials are reused, but MFA doesn’t apply.

What Completes the Picture?

To build real identity resilience, MFA needs support. Here’s what strengthens the whole chain:

1. Conditional Access Based on Risk

Don't just ask “Can they log in?”

Ask:

• Where are they logging in from?

• Is this a managed device?

• Is this behaviour typical?

Conditional access policies let you block, challenge, or log based on real-time risk—not just identity.

2. Session Control and Monitoring

Track what users do after they log in:

• Unusual data downloads

• Admin role activation

• Lateral movement across cloud services

Platforms that can inspect and control session behaviour (like MCAS, Sentinel, or other SIEMs) give insight beyond the login screen.

3. Least Privilege and Just-in-Time Access

Even with MFA, over-permissioned accounts are dangerous.

Use role-based access controls (RBAC), just-in-time elevation, and time-bound permissions to ensure users only get what they need—and nothing more.

This limits damage if an account is compromised.

4. User Education

People still approve prompts they shouldn’t. Train staff to:

• Spot MFA fatigue attacks

• Report suspicious behaviour

• Understand the why, not just the “how” of MFA

Good controls get better when users know how to use them.

Key Takeaway: Build Around MFA, Don’t Rely On It

MFA is critical. But it’s not a silver bullet. It’s one layer in a strategy that should include:

• Smart access decisions

• Ongoing monitoring

• Access governance

• User awareness

Don’t stop at the login screen. Security doesn’t end when someone clicks “approve.”

Final Thought: MFA Is Your Lock—But What About the House?

Think of MFA like a deadbolt on your front door. It’s important. But what if:

• The windows are open?

• The alarm is off?

• You’ve given everyone a spare key “just in case”?

• You never check who comes in?

That’s what relying on MFA alone looks like.

Secure identity means looking beyond the login—and building a model that assumes attackers will find a way in.

And when they do, it’s your other controls that determine what happens next.