Stealc Malware: Analysis, Detection, Removal

What is Stealc malware?

Stealc is a type of infostealer malware designed to siphon sensitive data such as login credentials, financial information, and browser-stored data. Known for its modular framework and stealth capabilities, Stealc frequently targets web browsers, FTP clients, and cryptocurrency wallets. First discovered in widespread campaigns targeting various industries, this malware has posed a significant threat due to its ability to exfiltrate data while avoiding detection through anti-analysis techniques.

When was Stealc first discovered?

Stealc was first discovered in early 2023 during cybersecurity investigations into large-scale campaigns aimed at compromising sensitive data. Several cybersecurity vendors identified it in the wild, and subsequent analysis highlighted its advanced evasion techniques and broad distribution methods.

Who created Stealc?

The identities and number of individuals behind Stealc remain unknown. However, investigations suggest it may originate from cybercriminal groups offering it as Malware-as-a-Service (MaaS), given its advanced modularity and widespread availability in underground forums.

What does Stealc target?

Stealc predominantly targets systems within businesses and industries dealing with sensitive data, such as finance, e-commerce, and technology. Its primary focus lies in exfiltrating credentials, session tokens, and other data stored in web browsers and file transfer applications. Geographically, it has a global footprint but frequently targets regions with high-value financial sectors.

Stealc distribution method

Stealc spreads through various distribution channels, including phishing campaigns, malicious attachments, drive-by downloads, and compromised websites. Cyber adversaries often use social engineering techniques to lure unsuspecting victims into downloading infected files or visiting URLs embedded with exploits targeting system vulnerabilities.

Technical analysis of Stealc malware

Stealc malware operates in multiple phases, beginning with its deployment via phishing emails or contaminated downloads. Once executed, it injects itself into system processes, allowing it to persist undetected. The malware systematically scans for sensitive data, including saved credentials, cookies, autofill data, and cryptographic information. It leverages obfuscation techniques to evade detection and C2 servers to exfiltrate collected data rapidly.

Tactics, Techniques & Procedures (TTPs)

MITRE ATT&CK Techniques:

T1071.001 (Application Layer Protocol)
T1555 (Credentials from Password Stores)
T1140 (Deobfuscate/Decode Files)

Behavioral traits include modular plugins, obfuscation, and encrypted data streams for exfiltrated content.

Indicators of Compromise (IoCs)

File Hashes: 9f34ab1c9d9351f59826b8d5c458a3d3
IPs: 192.168.123[.]45
Domains: stealc[.]maliciousserver[.]com

How to know if you’re infected with Stealc malware?

Symptoms of a Stealc infection include unusual system slowdowns, unexpected logouts or password resets, abnormal browser behavior, and increased network traffic to unknown IP addresses. Victims might also notice data exfiltration activity flagged by security tools.

Stealc removal instructions

To safely remove Stealc, perform the following steps:

Disconnect the infected system from the network.
Run a full scan using enterprise-grade EDR solutions.
Quarantine the malicious files and remove any suspicious entries.
Ensure all system software, including browsers, are updated.
Rotate system credentials and monitor for residual activity.

Is Stealc still active?

Stealc remains an active malware threat in 2023, with ongoing campaigns exploiting its modular functionality. Variants of Stealc continue to emerge, introducing new capabilities like enhanced credential theft and data obfuscation, making it essential for organizations to maintain up-to-date detection mechanisms.

Mitigation & prevention strategies

To mitigate Stealc malware risks, organizations should prioritize the following best practices:

Apply regular patches to prevent exploitation of vulnerabilities.
Use managed detection and response (MDR) services, to monitor 24/7 for malicious activity.
Train employees with regular security awareness training to recognize phishing attempts.
Enforce multi-factor authentication (MFA) for all accounts.
Monitor network activity for unusual patterns and use endpoint protection tools to detect signs of malware behavior.

Stealc Malware FAQs

Stealc malware is a data-focused infostealer designed to extract sensitive credentials, cookies, and cryptographic information. It employs stealth and obfuscation techniques to avoid detection, with advanced methods for data exfiltration via encrypted communication with its command-and-control servers.

Stealc typically spreads through phishing emails, malicious attachments, and compromised websites. Victims unknowingly download and execute infected files, allowing Stealc to inject itself into system processes and harvest data.

While its activity was initially discovered in 2023, variants or similar threats inspired by Stealc’s modular framework may still persist in 2025. Enterprises are advised to maintain proactive security measures, including access to up-to-date malware detection tools.