EXECUTIVE SUMMARY:
Marco Stealer is an information-stealing malware designed to compromise Windows systems and exfiltrate a broad range of sensitive data. Rather than focusing on disruption, the malware prioritizes stealth and data theft, targeting browser-stored credentials, cookies, session tokens, and cryptocurrency wallet information. It also expands its scope by collecting files from both local directories and cloud-synchronized storage locations, increasing the potential impact on individual users and enterprise environments alike. The malware demonstrates a clear emphasis on evasion, using encrypted strings and runtime decryption to conceal its true functionality from static analysis tools. Communication with external infrastructure is conducted in an encrypted manner, limiting the visibility of stolen data during transmission. These characteristics place Marco Stealer within a growing class of modern infostealers that are optimized for persistence, secrecy, and high-value data extraction rather than immediate monetization through destructive actions. By combining data harvesting, encryption, and evasive execution techniques, Marco Stealer reflects the continued evolution of credential-focused malware and highlights the increasing risks associated with browser-based authentication, cloud storage usage, and cryptocurrency adoption.
From a technical perspective, Marco Stealer follows a multi-stage execution flow designed to ensure reliability and resistance to analysis. Initial execution commonly involves a lightweight downloader that retrieves and launches the primary payload using scripting mechanisms. Once active, the malware establishes a mutex to prevent multiple instances from running simultaneously and performs environment checks to identify debugging tools or security software, terminating selected processes to obstruct investigation. Network connectivity checks are performed early in execution, allowing the malware to exit quietly if outbound communication is not possible. After validating execution conditions, the malware gathers system-level information such as hardware identifiers, operating system details, and network attributes to uniquely profile the infected host. Data collection routines are extensive, covering browser databases, extension directories linked to cryptocurrency wallets, clipboard contents, screenshots, and file systems associated with cloud-synced folders. Browser data extraction is achieved through advanced methods such as inter-process communication and injected components. All harvested information is encrypted individually before being transmitted to command-and-control servers, reducing the likelihood of interception and inspection by defensive tools.
Marco Stealer illustrates how information-stealing malware continues to advance in both capability and operational maturity. Its focus on credential theft, financial assets, and cloud-stored data demonstrates a shift toward maximizing long-term value from compromised systems rather than immediate exploitation. The malware’s extensive use of encryption, anti-analysis behavior, and selective execution conditions makes detection and investigation more challenging, particularly in environments lacking behavioral monitoring. By targeting commonly trusted data sources such as web browsers and synchronized storage folders, Marco Stealer exploits everyday user behavior to amplify its effectiveness. The threat also underscores the broader trend of malware developers refining their tools to bypass traditional security controls while maintaining flexibility across diverse environments. Although defensive technologies can still identify and block such threats when properly configured, the presence of malware like Marco Stealer reinforces the importance of layered security, continuous monitoring, and proactive threat hunting.
THREAT PROFILE:
| Tactic | Technique ID | Technique | Sub-Technique |
| Initial Access | T1566.001 | Phishing | Spearphishing Attachment |
| Execution | T1059.001 | Command and Scripting Interpreter | PowerShell |
| T1204.002 | User Execution | Malicious File | |
| Persistence | T1547.001 | Boot or Logon Autostart Execution | Registry Run Keys / Startup Folder |
| Defense Evasion | T1027.002 | Obfuscated Files or Information | Software Packing |
| T1070.004 | Indicator Removal | File Deletion | |
| T1562.001 | Impair Defenses | Disable or Modify Tools | |
| Credential Access | T1555.003 | Credentials from Password Stores | Credentials from Web Browsers |
| T1539 | Steal Web Session Cookie | — | |
| Discovery | T1082 | System Information Discovery | — |
| T1057 | Process Discovery | — | |
| Collection | T1115 | Clipboard Data | — |
| T1113 | Screen Capture | — | |
| T1005 | Data from Local System | — | |
| Command and Control | T1071.001 | Application Layer Protocol | Web Protocols |
| T1573.001 | Encrypted Channel | Symmetric Cryptography | |
| Exfiltration | T1041 | Exfiltration Over C2 Channel | — |
MBC MAPPING:
| Objective | Behaviour ID | Behaviour |
| Credential Access | B0028 | Cryptocurrency |
| Discovery | E1083 | File and Directory Discovery |
| Collection | E1056 | Input Capture |
| Defense Evasion | F0004 | Disable or Evade Security Tools |
| Execution | E1059 | Command and Scripting Interpreter |
| Command and Control | B0030 | C2 Communication |
REFERENCES:
The following reports contain further technical details:
https://securityonline.info/marco-stealer-the-new-data-raider-targeting-crypto-cloud-storage/
https://www.zscaler.com/blogs/security-research/technical-analysis-marco-stealer