How to Protect Identities and Sessions from Infostealers

Infostealers are among the most persistent and damaging strains of malware affecting individuals and organizations worldwide. These stealthy and malicious programs often go unnoticed, quietly infiltrating devices to steal sensitive data and relay it to cybercriminals. From session tokens and login credentials to financial information and browser-stored data, infostealers pose a grave risk to organizations. 

In this blog, we’ll provide a comprehensive overview of what infostealers are, how they operate, and the history of these threats. We’ll also dive into why some traditional security solutions and extension-based security solutions fall short in combating them. Finally, we’ll detail why CrowdStrike is uniquely positioned to defend against this consistent threat and deliver real identity security for modern organizations. 

What Is an Infostealer? 

An infostealer is a type of malware specifically designed to do what its name suggests: steal sensitive information. Often deployed through phishing emails, malicious downloads, compromised websites, or exploited vulnerabilities, infostealers can harvest: 

• Login credentials 
• Session tokens for active accounts 
• Browser-stored autofill data and cookies 
• Financial data, including credit card information and cryptocurrency wallets 
• System and network configurations 

Infostealers differ from threats like ransomware because they operate quietly in the background. They often go undetected while transmitting the data they harvest to a remote command-and-control (C2) server. Infostealers are particularly dangerous because they can lead to identity theft through session hijacking, which enables threat actors to use stolen session tokens to impersonate users and access sensitive systems via their login credentials without requiring a multifactor authentication (MFA) challenge or the victim’s password. 

The History of Infostealers 

Infostealers have been an active threat since the mid 2000s. Often credited as the first widespread infostealer is the infamous Zeus virus, aka Zbot. Zeus infected devices via phishing and drive-by downloads, targeting financial institutions to capture banking credentials. Since then, infostealers have evolved greatly in sophistication, scale, and intensity.  

Here are some notable infostealers that have made their way onto devices over the years: 

• Zeus (2007-2010): Pioneered modern identity security threats with its ability to intercept online banking sessions 
• Emotet (2014-2021): Initially a banking trojan, later expanded to deliver other malware including infostealers 
• Racoon Stealer (2019-present): Sold as malware as a service, targeting browsers, email clients, and cryptocurrency wallets 
• Lumma Stealer (2023-present): Compromised hundreds of thousands of devices by stealing browser-stored credentials and session tokens 

This malware category has thrived due to the value of stolen credentials and session hijacking opportunities on underground markets. A single valid session token for a corporate system can be worth tens of thousands of dollars on dark web forums. 

How Infostealers Operate: Tactics and Timeline 

The infostealers most used today typically follow a lifecycle like the following:  

• They are delivered through phishing emails, malvertising, pirated software, or apps with vulnerabilities 
• The infostealer’s payload installs quietly in the background, avoiding detection by traditional antivirus solutions 
• Once installed on a device, the infostealer begins harvesting data like session tokens, cookies, credentials, and financial details 
• After collecting data, the infostealer transmits the information to the attacker’s remote infrastructure 
• After exfiltration, some infostealers will remain persistent, maintaining access for ongoing surveillance and data theft

Consequences of an Infostealer Attack 

The impact of an infostealer attack can be devastating. Because infostealers quietly extract sensitive data, organizations often remain unaware until significant damage has been done. Here are some of the most serious consequences organizations can face: 

Account Takeover via Session Hijacking

Session hijacking is arguably the most dangerous. By stealing session tokens, attackers can impersonate legitimate users without needing their passwords. This means even accounts protected by multifactor authentication can be compromised. From corporate email accounts to cloud dashboards and financial portals, these unauthorized logins can lead to data leaks, financial theft, and unauthorized transactions.

Credential Theft and Identity Fraud

Infostealers harvest login credentials stored in browsers, including those for email, banking, cloud services, and social media accounts. This sensitive information is often sold on the dark web, giving way to identity fraud. Attackers may open new accounts in a victim’s name, conduct unauthorized purchases, or initiate scams.

Data Breaches and Compliance Violations

When a threat actor hijacks session tokens, they gain access to sensitive corporate data, intellectual property, and potentially customer information. A single compromised session can lead to a major data breach. This often results in regulatory penalties under data protection laws, reputational damage, and legal liabilities.

Financial Losses

Infostealers can extract financial data, credit card numbers, and cryptocurrency wallet keys unnoticed. The direct financial impact can be immediate, as attackers drain wallets or make unauthorized transactions. Additionally, the costs of incident response, system restoration, legal actions, and customer notification can amount to millions of dollars for affected businesses. 

Long-Term Brand and Trust Damage

Victims of infostealer attacks often suffer long-term reputational harm. Clients, partners, and customers may lose trust in a company’s ability to protect sensitive data, leading to lost contracts, customer churn, and competitive disadvantage. 

Why Extension-Based Security Solutions Can’t Stop Infostealers 

Today, some enterprise organizations rely on browser extension-based security tools to shore up their identity security. While these solutions can sometimes provide valuable features such as phishing protection and the management of cookies, they are fundamentally limited in their ability to counter advanced infostealers. They have limited access to browser internals, no control over HTTP traffic, often only focus on cookie protection, and tend to be reactive in nature.

How CrowdStrike Stops Infostealers and Session Hijacking 

Protecting against session hijacking, session token theft, and identity-based attacks requires a fundamentally different approach. CrowdStrike’s browser security technology operates inside the browser itself. We offer:

Deep Browser Integration

CrowdStrike integrates directly into the browser environment, giving it privileged access to internal session storage, runtime data, and session management processes. This allows us to actively monitor, secure, and encrypt session tokens before they can be stolen.

Comprehensive Identity Security

CrowdStrike’s solution goes beyond cookie protection to protect all browser-stored credentials, autofill data, session tokens, and sensitive transaction data. Our real-time threat detection engine identifies unauthorized data exfiltration attempts and halts them before damage occurs.

Real-Time Session Hijacking Prevention

By continuously validating the integrity and security context of active sessions, CrowdStrike prevents attackers from using stolen session tokens to gain access to systems. If a suspicious session is detected, it’s immediately invalidated and the user is alerted.

HTTP Traffic Visibility

CrowdStrike’s technology provides secure oversight of HTTP and HTTPS communications without compromising user privacy. This allows for the detection of anomalous traffic patterns associated with infostealers and the prevention of data exfiltration over encrypted channels.

Adaptive Threat Response

The CrowdStrike Falcon® platform uses advanced behavioral analytics and machine learning to identify previously unknown infostealers, including zero-day variants. CrowdStrike stops threats dynamically, even when no signature or indicator of compromise exists. 

The Future of Identity Security

Infostealers represent one of the fastest growing and most dangerous classes of malware out there today. Their ability to harvest login details, session tokens, and sensitive personal data makes them a formidable threat to both individuals and enterprises. While browser extension-based security tools offer partial protection, they are fundamentally incapable of stopping advanced infostealers due to limited browser access, no control over HTTP traffic, and narrow cookie-focused defenses. 

CrowdStrike delivers a proactive, deeply integrated browser protection solution that ensures real identity security, prevents session hijacking, and stops infostealers before they can do harm.

Additional Resources

• Interested in learning more? Join us at Fal.Con 2026, where these conversations take center stage.
• Learn about CrowdStrike Falcon® Secure Access browser security.