One of the most persistent and damaging strains of malware affecting individuals and organizations worldwide is the infostealer. 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 fact, the average cost of a data breach globally reached over $4.88 million last year.
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 Seraphic Security 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 (usernames and passwords)
- 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 other malicious 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. Session hijacking enables threat actors to use stolen session tokens to impersonate users and access sensitive systems via their login credentials.
The History of Infostealers
Malware as a concept is nothing new, and infostealers have been an active threat since the mid 2000s. Often credited as the first widespread infostealer is the infamous Zeus virus a.k.a. Zbot. Zeus infected devices via phishing and drive-by-downloads targeting financial institutions to capture banking credentials. Since Zeus hit the scene, 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 (MaaS), targeting browsers, email clients, and cryptocurrency wallets.
- Lumma Stealer (2023-2025): Lumma 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 hundreds 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 will begin to harvest data like session tokens, cookies, credentials, and financial details.
- After collecting data, the infostealer will transmit the information to the attacker’s remote infrastructure.
- After exfiltration, some infostealers will remain persistent, maintaining access for ongoing surveillance and data theft.
- One key tactic often used by infostealers is session hijacking. Session tokens are small pieces of data used to authenticate someone’s identity without actually having them login. By hijacking session tokens, attackers can bypass security protocols to gain unauthorized access to accounts and systems.
Consequences of An Infostealer Malware Attack
The impact of an infostealer malware 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 face after an infostealer incident:
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 that even accounts protected by multi-factor authentication (MFA) 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 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, IP, 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 virtually 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. Here’s why:
- Limited Access to Browser Internals: Browser extensions operate within strict sandbox environments for security and privacy reasons. They do not have access to internal session storage where session tokens reside. This means extensions cannot monitor, protect, or encrypt these critical tokens, leaving them vulnerable to theft.
- No Control Over HTTP Traffic: Infostealers often intercept and extract sensitive data during HTTP transactions. Browser extensions cannot read, modify, or encrypt HTTP or HTTPS traffic in transit, which is a major blind spot when attackers harvest data mid-session.
- Cookie-Only Focus: Many extension-based solutions focus solely on cookie protection, ignoring other vital areas such as autofill data, browser storage, and session tokens. Infostealers target a broader range of data beyond just cookies.
- Reactive, Not Proactive: Extensions typically rely on static threat signatures or known malicious URLs. Modern infostealers use dynamic C2 infrastructure and encrypted communication, which allows them to evade detection by conventional extension-based security measures.
The bottom line: Extension-based security solutions cannot stop infostealers because they lack the necessary visibility, control, and integration within the browser environment.
Why Seraphic Security Is Uniquely Positioned to Stop Infostealers and Session Hijacking
At Seraphic Security, we understand that protecting against session hijacking, session token theft, and identity-based attacks requires a fundamentally different approach. That’s why we’ve developed a next-generation browser security platform that operates where it matters most, inside the browser itself.
Deep Browser Integration
Unlike security extensions, Seraphic 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
Seraphic’s solution goes beyond cookie protection. We 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, Seraphic 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
Seraphic’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
Our platform uses advanced behavioral analytics and machine learning to identify previously unknown infostealers, including zero-day variants. Seraphic stops threats dynamically, even when no signature or indicator of compromise exists.
The Future of Identity Security in a Post-Infostealer Era
As infostealers become more sophisticated and accessible through Malware-as-a-Service offerings, the importance of effective identity security solutions will only increase. Businesses can no longer rely solely on endpoint detection or extension-based browser protection to defend against session hijacking and data theft.
The recent takedown of the Lumma Stealer network by Microsoft and the FBI highlights both the scale of the threat and the critical need for modern, integrated security solutions. At Seraphic Security, we’re committed to staying ahead of emerging threats by providing innovative, browser-native security that stops infostealers at the source, before they can compromise your session tokens, identities, and digital assets.
Conclusion
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.
Seraphic Security delivers a proactive, deeply integrated browser protection solution that ensures real identity security, prevents session hijacking, and stops infostealers before they can do harm. To learn more about how Seraphic can safeguard your organization against the next wave of browser-based threats, schedule a demo today.
