Multi-factor authentication (MFA) is widely seen as the gold standard in cybersecurity. For many small and mid-sized businesses, especially those relying on Microsoft 365 or Google Workspace, enabling MFA authentication feels like a critical win in protecting against modern threats. And it is—but only up to a point.
There’s a growing threat that slips past even the most vigilant MFA strategies: session token theft.
This method doesn’t steal passwords—it steals tokens representing already-authenticated sessions. Think of it like someone lifting your digital guest pass—they don’t need to know your password if they have the badge that lets them walk right in.
These types of attacks—often part of a broader tactic known as session hijacking—can allow a threat actor to gain access to your systems and data without ever triggering another authentication request.
In this article, we’ll explain how token theft attacks work and how to stop them before they cause real damage.
What Is a Session Token?
A session token is a temporary credential that confirms you’ve already passed the authentication checks, such as entering your password and completing MFA. Systems like Microsoft 365 use session tokens to keep you logged in across apps and services without requiring you to verify your identity repeatedly.
Think of a session token like a digital guest pass at a secure office. Once you’ve been given that pass, you can move around freely without showing ID at every door. It’s convenient, but if someone else gets that pass, they can do the same without being challenged again.
Most systems, including Microsoft Entra ID, issue refresh tokens that automatically extend access as long as activity continues. These tokens can last days—or even up to 90 days—meaning that once a token is compromised, a threat actor has ample time to exploit that user session.
Understanding what a session token is makes it easier to see how attackers use them in token theft attacks.
Real-World Scenario: How Session Token Theft Works
To understand the severity of session token theft, it helps to walk through a real-world example. Here’s how a typical token theft attack might unfold:
Step 1: The Phishing Email
A user receives a phishing email that appears urgent and convincing. It might claim to be from Microsoft or a colleague and urge the recipient to view a document or respond to a critical request.
Step 2: The Fake Login Page
Clicking the link takes the user to a spoofed Microsoft 365 login page. It looks authentic, but it’s controlled by a threat actor running an adversary in the middle attack.
Step 3: Entering Credentials
The user enters their email and password into the fake site. Everything still looks legitimate.
Step 4: Approving the MFA Prompt
The site forwards the real MFA request to the user. The user approves it, thinking they’re logging in securely, unknowingly validating access for the attacker.
Step 5: Stealing the Token
Behind the scenes, the attacker captures the credentials and the session token issued after successful authentication. This token is the real prize—it lets them gain access without repeating MFA authentication.
Step 6: Redirecting the User
To avoid suspicion, the attacker redirects the user back to the real Microsoft login page. The user assumes the login failed and tries again, unaware they’ve just been compromised.
Step 7: Using the Stolen Token
The attacker now uses the stolen token to log in to office.com or other Microsoft 365 services. Since the token is valid, Microsoft sees it as a trusted user session and skips MFA.
Step 8: Exploiting the Session
With this access, the attacker can:
- Send emails as the user, tricking colleagues or clients.
- Upload/share malicious files via OneDrive or SharePoint.
- Exfiltrate or manipulate data that the user has access to.
- Change financial details or internal configurations.
- Damage reputation through mass messaging or suspicious activity.
Because Microsoft’s default token lifespan is up to 90 days, the attacker may remain undetected for weeks—unless proactive monitoring is in place.
Omega’s service can detect a session token theft in less than eight minutes and suspend the account long before an attacker has the chance to cause real damage.
Why MFA Alone Isn’t Enough
Multi-factor authentication (MFA) is a powerful defense mechanism—but it’s only effective at a specific moment: when the user signs in. Once that check is passed, a session token is issued, and that token becomes the user’s ongoing authentication method.
The problem? If a threat actor manages to steal tokens, they can gain access without needing to reauthenticate. MFA authentication doesn’t get triggered again because, from the system’s point of view, the user has already been authenticated.
Recent insights from Microsoft Entra show just how widespread identity attacks have become. Over 600 million identity-based attacks occur daily, with more than 99% targeting passwords. In fact, Microsoft blocks an average of 7,000 password attacks per second, illustrating the scale and persistence of these threats.
As user agent strings, IP addresses, and sign-in events can appear legitimate, detection requires more than standard monitoring—it demands a layered security approach.
MFA is necessary, but not sufficient. Businesses need to look beyond it to secure every aspect of the user session lifecycle.
How MSPs Help Prevent and Detect Token Theft
Detecting and mitigating session token theft requires specialized tools and expertise—something many small and mid-sized businesses may not have in-house. That’s where Managed Service Providers (MSPs) like Omega Network Solutions play a crucial role.
Omega uses a proactive, layered approach to identify and stop token-based threats by monitoring:
1. User Sign-In Events
By analyzing every sign-in event, Omega can detect patterns that deviate from a user’s norm. For example, a login from a previously unseen IP address or unusual geography could trigger alerts.
2. Conditional Access via Microsoft Entra ID
Microsoft Entra ID allows conditional access policies that restrict access based on criteria like device health, location, or risk level. These rules prevent attackers from easily exploiting stolen tokens.
3. User Agent Strings and Session Behavior
Omega flags inconsistencies in user agent strings (like browsers or devices never used before) and correlates them with session times and activity to uncover suspicious behavior.
4. Real-Time Monitoring and Automated Response
Using behavior-based detection systems, Omega can identify and suspend anomalous user sessions within minutes, often before any damage occurs.
Omega’s unique strength lies in our ability to detect and suspend compromised accounts in under eight minutes, minimizing exposure and limiting fallout.
5. Education and Prevention
Omega also helps train users to recognize phishing and social engineering tactics, reducing their chances of falling for attacks that lead to token theft.
Together, these layers form a resilient defense that evolves to meet threats as they emerge.
Employee Awareness Is Part of the Solution
Even with the best technology, employees remain a critical line of defense. In most token theft attacks, it’s not software that fails—it’s human judgment. A well-crafted phishing email can still trick someone into handing over their credentials and approving an MFA prompt, especially if they don’t understand what’s happening.
Attackers know this. They exploit urgency, fear, or curiosity to manipulate users into fast, unthinking responses. For example, a message that appears to come from a supervisor or IT, urging immediate action, can override cautious instincts.
That’s why Omega Network Solutions includes user training and simulated phishing exercises in our cybersecurity programs. Teaching users to pause, verify links, and recognize common red flags can dramatically reduce the risk of session token theft and other cyberattacks.
Awareness doesn’t just support your tools—it multiplies their effectiveness.
Is Your Business Protected from Session Token Theft?
Cybersecurity isn’t just about checking a box—it’s about understanding evolving threats and staying ahead of them. As we’ve seen, MFA is no longer enough on its own to stop modern token theft attacks.
Let’s recap:
- Session token theft allows attackers to hijack authenticated user sessions and bypass MFA authentication.
- These attacks often use phishing and adversary-in-the-middle tactics to trick users and steal tokens.
- Once compromised, attackers can gain access, impersonate users, and cause serious harm, often undetected.
- Omega Network Solutions can detect these threats in under 8 minutes, using advanced monitoring, behavior-based detection, and user training.
You don’t need to face this threat alone. With Omega, your business gains a trusted partner with the tools and expertise to stop session hijacking before it impacts your operations.
Book Your Free Cybersecurity Assessment
Want to know if your security stack is vulnerable to session token theft? Book a free cybersecurity assessment with Omega Network Solutions today. Discover where your current defenses fall short—before attackers do.