Microsoft MFA AuthQuake Flaw: Unlimited Brute-Force Attacks Without Detection. Here is what to know.

A critical vulnerability in Microsoft’s Multi-Factor Authentication (MFA) system, dubbed AuthQuake, has been discovered by cybersecurity researchers from Oasis Security. This flaw allowed attackers to bypass MFA protections and gain unauthorized access to user accounts, including Outlook emails, OneDrive files, Teams chats, and Azure Cloud resources.

How Researchers Discovered the AuthQuake Vulnerability

Oasis Security identified the vulnerability in June 2024. AuthQuake stemmed from two key issues: a lack of rate limiting and an extended timeframe for validating Time-Based One-Time Password (TOTP) codes. Attackers could rapidly create new sessions and attempt multiple code guesses simultaneously, quickly exhausting all possible 6-digit code combinations.

This flaw was particularly alarming as it exploited fundamental weaknesses in the MFA system, making it an easy target for attackers.

The Significant Impact of AuthQuake on User Accounts

The vulnerability was particularly dangerous because it required no user interaction and generated no alerts, leaving account holders completely unaware of the ongoing attack. This stealthy nature made it possible for attackers to breach accounts within approximately 70 minutes, achieving a success rate exceeding 50%.

Users were left vulnerable, and sensitive information was at risk, highlighting the need for better safeguards.

Microsoft’s Swift Response to the AuthQuake Flaw

Upon being notified, Microsoft swiftly acknowledged the issue and implemented a temporary fix in July 2024. By October 2024, a permanent solution was deployed, introducing stricter rate-limiting mechanisms that activate after a number of failed attempts. This fix significantly reduced the risk of brute-force attacks.

Microsoft’s response underscored the importance of swift action in the face of security threats, ensuring that users’ data remained protected.

Lessons Learned from the Microsoft AuthQuake Vulnerability

The AuthQuake vulnerability highlights the importance of robust MFA implementations. Security experts recommend:

• Enforcing limits on failed authentication attempts.
• Setting up alerts for repeated second-factor authentication failures.
• Conducting regular security audits.

Additionally, educating users on the importance of MFA and how to use it effectively is crucial. Organizations must ensure that their security protocols are up to date and continuously monitored.

Conclusion

While the AuthQuake flaw has been addressed, it serves as a reminder that security isn’t just about deploying MFA—it must also be configured properly. Organizations are advised to continue using MFA, preferably with authenticator apps or stronger passwordless methods, while staying vigilant against potential vulnerabilities.

This incident underscores the need for constant vigilance and proactive measures in cybersecurity.

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