What Is an Infostealer?

An infostealer (also information stealer or info stealer) is a type of malware designed to covertly infiltrate computer systems and exfiltrate sensitive data to remote servers controlled by threat actors. Infostealers steal login credentials, cookies, financial data, personally identifiable information, and authentication tokens from victim devices. Modern infostealers increasingly target two-factor authentication tokens, passkeys, and cryptocurrency wallets, operating through a Malware-as-a-Service model that democratizes access to sophisticated credential theft capabilities.

How does an infostealer work?

Infostealers operate through sophisticated data collection, technical architecture, and rapid exfiltration mechanisms designed to steal maximum data before detection.

Data collection methods target multiple sources on victim devices. According to SpyCloud (2025), authentication data including usernames, passwords, session cookies, and authentication tokens stored in browsers represents the primary target. Financial information such as credit card numbers and bank account details provides immediate monetization opportunities. Personal identifiers including Social Security numbers, addresses, and phone numbers enable identity theft. Emerging targets include two-factor authentication tokens, passkeys, and cryptocurrency wallet credentials.

The technical architecture typically uses a two-part system. According to PacketLabs (2024), a bot framework or builder tool allows threat actors to configure infostealer behavior and define what data to steal. The framework includes modules for keylogging, form grabbing, and clipboard hijacking. A command-and-control server—often written in PHP, HTML, and JavaScript—is hosted on commercial cloud infrastructure and receives exfiltrated data from infected devices.

Data collection techniques vary by sophistication. Keylogging records all keystrokes entered by the user. Form grabbing intercepts data submitted through web forms before browser encryption occurs. Clipboard hijacking steals or replaces information stored in the user's clipboard. Browser credential harvesting extracts stored passwords from browser password managers.

Infection and distribution leverage multiple vectors. According to Malwarebytes Labs (2024), distribution vectors include phishing emails, malicious links, SEO poisoning, drive-by downloads, compromised YouTube links, infected game mods, and malicious advertisements. The delivery model commonly uses Malware-as-a-Service, enabling operators with varying technical skill to deploy infostealers.

Non-persistent execution is a distinguishing characteristic. According to SpyCloud and KELA Cyber, infostealers execute and can remove themselves within seconds, leaving minimal forensic evidence. This rapid execution complicates detection and incident response because the infection may be gone before security tools detect it.

How does an infostealer differ from related threats?

Infostealers are distinct from other malware because they focus primarily on data exfiltration rather than system destruction, operate stealthily with minimal system impact to avoid detection, and are commonly distributed via Malware-as-a-Service that democratizes their use. They serve as facilitators for downstream attacks including ransomware and lateral movement.

Form grabbers represent a subset of infostealer functionality, focusing specifically on intercepting web form data. Keyloggers are often included in infostealer capabilities but infostealers are broader in scope, targeting multiple data sources beyond just keystrokes. Infostealers are the primary tool for large-scale credential harvesting campaigns.

Infostealers frequently serve as initial access malware, providing entry points for ransomware and other secondary attacks. According to multiple threat intelligence reports, credentials stolen by infostealers are sold on criminal forums and used by other threat actors to gain initial access to organizations for ransomware deployment.

The Malware-as-a-Service model distinguishes infostealers operationally. Three groups participate: developers who write code, service providers who sell licenses, and operators who deploy infostealers. This model enables less-skilled threat actors to conduct sophisticated attacks.

Why do infostealers matter?

Infostealers represent a fundamental and growing threat that enables a broad range of downstream attacks and data breaches.

A study by Hadrian and Passguard found that 64% of mid-to-large enterprises had at least one infostealer infection resulting in compromised credentials appearing on the dark web in the last five years. Organizations suffered an average of 4.5 infostealer infections over a 12-month period according to the same study.

KELA Cyber reports that infostealer attacks rose 58% during 2024. According to SpyCloud research (2025), nearly 50% of all corporate users were compromised by infostealers.

The credential scale is staggering. SpyCloud recaptured 63.8 billion distinct identity records in 2025, representing a 24% year-over-year increase. According to Vectra AI (2025), infostealers collectively stole 1.8 billion credentials during 2025.

Analysis of 300 compromised machines infected with infostealer malware from July-August 2024 contained more than 100,000 compromised credentials, according to SpyCloud research. This demonstrates the scale of credential theft from even limited infections.

Dominant malware families show rapid evolution. LummaC2 surged from less than 1% market share in 2023 to 31% by late 2024, becoming the most prevalent infostealer variant according to multiple threat intelligence reports. Vidar Stealer represents approximately 17% of infostealer incidents in late 2024 and stole over 65 million passwords in six months.

The ransomware connection is significant. According to the 2025 Verizon Data Breach Investigations Report, stolen credentials were the initial access vector in 22% of breaches, and 88% of basic web application attacks involved stolen credentials, often sourced from infostealer malware. This demonstrates that infostealers enable subsequent attacks rather than being standalone threats.

Endpoint security bypass is concerning. At least 54% of devices infected with infostealer malware had antivirus or EDR solutions installed at the time of infection, according to SpyCloud and threat intelligence reports (2024). This highlights how infostealers bypass traditional defenses through rapid execution and memory-resident techniques.

What are the limitations of infostealers?

Infostealers face several detection and operational challenges that constrain their effectiveness.

Detection and forensics challenges stem from minimal forensic evidence. According to SpyCloud (2025), infostealers execute in-memory and can remove themselves within seconds, leaving little evidence on disk for forensic analysis. Endpoint protection limitations mean that 66% of malware infections occur on devices with endpoint security solutions already installed, indicating traditional signature-based detection is insufficient.

No persistent artifacts distinguish infostealers from other malware. Unlike many malware types, infostealers do not require persistence mechanisms such as registry entries or scheduled tasks, making detection harder through traditional indicators of compromise.

Defense gaps include browser credential storage weakness. Many browsers store passwords locally by default, making them easy targets for infostealers despite being a known risk. Two-factor authentication bypass capability exists because infostealers can steal session cookies and 2FA tokens, partially circumventing MFA protections. Cloud infrastructure abuse means infostealers' command-and-control servers are often hosted on legitimate cloud providers, making blocking them difficult without impacting legitimate services.

Operational weaknesses affect attacker effectiveness. Noise in exfiltrated data means not all stolen credentials are immediately actionable—many may be stale or non-functional, reducing attacker return on investment. Malware-as-a-Service operator variability creates quality and operational security variance among operators, creating an inconsistent threat landscape.

Multi-factor authentication provides partial protection. While infostealers can steal session cookies and 2FA tokens, properly implemented phishing-resistant MFA such as FIDO2 hardware keys cannot be captured through credential theft alone.

How can organizations defend against infostealers?

Organizations should implement layered technical controls, monitoring capabilities, and process improvements to detect and mitigate infostealer threats.

Endpoint Detection and Response should deploy EDR solutions with behavioral analysis capabilities to detect anomalous activity rather than relying solely on signatures. According to Check Point Software and Microsoft Security Blog (2025), monitoring should focus on processes accessing browser credential stores or Windows Credential Manager in unusual ways. Detection of unusual process spawn chains and memory-resident execution patterns identifies infostealers during execution.

Memory and Network Forensics capabilities detect infostealers operating entirely in RAM. According to Vectra AI (2025), deploying Network Detection and Response solutions identifies suspicious data exfiltration patterns. Monitoring for unauthorized outbound connections to command-and-control servers catches infostealers during the exfiltration phase.

Credential Protection begins with disabling password saving in web browsers via Group Policy Objects or security policies. According to SpyCloud, organizations should implement multi-factor authentication as a failsafe against stolen credentials and use password managers with strong encryption and zero-knowledge architecture. Monitoring for browser credential store access and Windows Credential Manager queries provides early warning of credential theft attempts.

Digital Risk Protection implements continuous dark web and paste site monitoring for exposed corporate credentials. According to Check Point and Vectra AI, organizations should establish post-infection remediation processes to identify compromised credentials before attackers exploit them. Integrating threat intelligence feeds identifies new infostealer families and attack patterns.

SIEM and SOAR Integration consolidates logs into Security Information and Event Management solutions. According to SpyCloud, using Security Orchestration, Automation, and Response for automated response to detected threats improves reaction time. Real-time dashboards for network visibility enable security teams to identify anomalous patterns.

Security awareness training educates employees to recognize phishing emails, malicious downloads, and social engineering attacks. According to Microsoft Security Blog and Check Point, user education reduces initial infection rates by helping users avoid the delivery mechanisms infostealers rely on.

Incident response procedures establish clear processes for credential revocation and account recovery following suspected infostealer infections. Organizations should maintain accurate asset inventories and prioritize protection based on data sensitivity.

Browser security policies should restrict or disable password storage in browsers, particularly for privileged accounts. Organizations should deploy enterprise password managers instead of relying on browser-based credential storage.

Network segmentation and Zero Trust architecture limit the impact of stolen credentials by requiring additional verification beyond usernames and passwords. Even if credentials are stolen, network segmentation prevents lateral movement to sensitive systems.