Understanding how infostealers operate, why MFA won't always save you, and what your business must do to adapt is critical to protecting your digital footprint.
For years, cyber security advice for small and medium-sized businesses followed a predictable playbook: create complex passwords, don’t write them down, and turn on Multi-Factor Authentication (MFA).
If you did those three things, you were told your digital front door was locked.
Today, that playbook is dangerously outdated. Cyber criminals are no longer wasting time trying to crack or guess passwords. Instead, they are deploying a class of malware known as Infostealers and using them to bypass MFA entirely by hijacking your active browser sessions.
Understanding how infostealers operate, why MFA won't always save you, and what your business must do to adapt is critical to protecting your digital footprint.
What Is Infostealer Malware?
Infostealer malware, with infamous strains such as Lumma Stealer, Vidar, and RisePro is malicious software purpose-built to harvest data from compromised devices.
Unlike ransomware, which immediately encrypts files and demands a ransom, an infostealer operates silently in the background. It quickly scoops up saved passwords, browser autofill data, crypto wallet keys, and most importantly active browser session cookies and JSON Web Tokens (JWTs).These stealers infect devices through deceptive tactics such as Fake CAPTCHA / "ClickFix" Lures where users are prompted to verify they are human by running a quick terminal or PowerShell command that silently installs the payload in memory.
How Session Hijacking Bypasses MFA
To understand why MFA fails against session hijacking, consider how web logging works:
The Standard Login: An employee logs into a cloud application (e.g., Microsoft 365, Google Workspace, Salesforce) using their username, password, and an MFA prompt (a push notification or SMS code).
The Session Cookie: Once identity is proven, the server issues a digital "passport"—a session cookie or authentication token—to the user's web browser. This token tells the server: "This user is already fully authenticated; do not ask them for a password or MFA again for the rest of the session."
The Theft: When an infostealer infects the machine, it copies those active session cookies straight out of the browser's database and exfiltrates them to the attacker's command server.
The Replay: The cybercriminal imports those stolen session cookies into their own browser.
Because the application sees a valid, active session token, it lets the attacker straight into the account without asking for a password or sending an MFA prompt.
The attacker walks right through the front door using your legitimate digital identity.
The Dark Web "Stealer Log" Economy
Infostealer developers operate under a low-cost Malware-as-a-Service (MaaS) business model. Once malware operators harvest these session packages, they package them into "stealer logs" and sell them on underground forums, Telegram channels, and dark web marketplaces.
Initial Access Brokers (IABs) and ransomware groups buy these logs specifically to target corporate networks. A single stolen Single Sign-On (SSO) session cookie from an un-managed home laptop or contractor workstation can give an attacker direct access to an entire enterprise environment in under 48 hours.
Why SMBs Are Particularly Exposed
Large corporations spend tens of thousands of pounds on complex Identity Threat Detection and Response (ITDR) systems to spot anomalous session token usage. SMBs rarely have those resources, leaving them open to distinct operational blind spots. With BYOD & Remote Workers employees are accessing corporate cloud drives or emails from personal devices where infostealers are most commonly contracted.
Modernizing Your Defense Strategy
Relying solely on passwords and basic MFA is no longer enough. To protect against infostealers and session hijacking, SMBs should adopt a multi-layered identity defense:
Shorten Session Lifetimes: Configure cloud identity providers (like Microsoft Entra ID or Google Workspace) to enforce shorter session idle times and re-authenticate high-risk actions.
Restrict Unmanaged Devices: Implement conditional access policies so employees can only access core business systems from managed, secure devices.
Monitor Underground Exposures: Continuously monitor dark web forums and criminal marketplaces for leaked corporate session logs and credentials.
How CyberSentrx Stops Session & Credential Threats
When an infostealer harvests tokens or credentials tied to your corporate domain, speed is everything. Revoking an exposed session before a threat actor replays it is the difference between a routine cleanup and a full-scale corporate breach.
At CyberSentrx, we build automated dark web scanning and external threat intelligence tools designed specifically for small and medium-sized UK businesses. We continuously monitor illicit underground networks, paste sites, and stealer-log dumps for your corporate domains—alerting you immediately if exposed credentials or session data surface.
Don't wait for a hijacked session to disrupt your operations.
Run a Free Exposure Check with CyberSentrx to discover what external risks and leaked credentials may be lurking in your corporate footprint today.