Multi Factor Authentication (MFA) is one of the most important security steps a business can take. By requiring a second form of verification beyond a password, it blocks the vast majority of account takeover attempts. However, a sophisticated technique called “session hijacking” or “token theft” is increasingly being used to bypass MFA, making it a top threat for 2026.
What is Session Hijacking?
In simple terms, when you log into an application (like Microsoft 365 or your bank), your browser receives a temporary “key” called a session cookie. This key tells the application you are already authenticated, so you do not have to enter your password and MFA code repeatedly.
Session hijacking occurs when malware on your device steals this session cookie. The attacker then uses that stolen cookie in their own browser to impersonate you, gaining full access to your account without ever needing your password or MFA code. Your MFA was successfully completed, but the criminal stole the “key” that proves it.
How to Harden Your MFA Against This Threat
The good news is that you can significantly reduce the risk of session hijacking by adjusting a few key settings, primarily within your Microsoft 365 or Google Workspace environment.
- Enforce Conditional Access Policies:
This is your most powerful defense. Conditional Access allows you to set rules that define how and from where users can access company data. Key policies to implement include: - Require Compliant Devices: Block access unless the login is coming from a company managed and secured device (e.g., one with encrypted disks and up to date antivirus).
- Block Legacy Authentication: Disable older, less secure authentication protocols that do not support modern MFA and are easy to exploit.
- Set Location Based Rules: If your business operates in one country, you can block login attempts from high-risk countries.
- Shorten Session Timeouts:
A session that lasts for 30 days is a much bigger target than one that lasts for an hour. Reduce the sign in frequency for your users. Forcing re authentication more often limits the window of opportunity for a stolen session cookie to be useful. A good balance between security and user convenience is a 4-to-8-hour timeout for low-risk applications. - Leverage Risk-Based Authentication:
Platforms like Microsoft Entra ID (formerly Azure AD) can detect suspicious login signals, such as an attempt from an unfamiliar location, an anonymous IP, or a device with malware present. You can configure your MFA system to require an additional verification step when these high-risk signals are detected, effectively blocking a hijacked session. - Invest in Advanced Endpoint Security:
Since session hijacking often starts with malware, robust endpoint protection is non-negotiable. A modern Endpoint Detection and Response (EDR) solution can detect and quarantine the malware designed to steal session cookies before it can do its job.
Taking these steps moves your MFA from a simple gatekeeper to an intelligent, adaptive system. For a deeper dive into configuring these settings, Microsoft provides an excellent guide on Conditional Access best practices.
Is your MFA configured to stop modern threats like session hijacking? Our security experts can audit your current setup and ensure your policies are hardened against evolving attacks. Contact us for a quick MFA health check.
