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Cybercriminal groups are constantly evolving their tactics to breach enterprise networks, and FIN7 is no exception. The notorious hacking group, known for its financially motivated cyberattacks, has recently been observed deploying the Anubis backdoor to hijack Windows systems. This latest campaign involves exploiting compromised Microsoft SharePoint sites to distribute malicious payloads, marking a new level of sophistication in their attack strategies.

This article explores FIN7’s history, the functionalities of the Anubis backdoor, the attack methodology, and ways to mitigate such threats. Given the increased reliance on SharePoint and cloud collaboration platforms, understanding this threat is crucial for businesses and security professionals.

Who is FIN7?

FIN7, also known as Carbanak Group or Navigator Group, is a well-established cybercriminal organization specializing in financial fraud, ransomware attacks, and espionage. Active since at least 2015, the group has targeted businesses worldwide, especially in banking, hospitality, and retail sectors. Over the years, FIN7 has leveraged advanced malware strains, including Carbanak, and has developed tactics to evade security measures.

FIN7’s Notorious Activities

FIN7 has a history of highly sophisticated cyberattacks, often blending traditional hacking techniques with social engineering. Some of their notable campaigns include:

• Point-of-Sale (PoS) Attacks: FIN7 has targeted PoS systems in retail and hospitality businesses, stealing credit card data from millions of customers.
• Ransomware Deployments: The group has been linked to ransomware families like REvil and DarkSide, weaponizing financial extortion.
• Supply Chain Attacks: FIN7 has infiltrated software vendors to compromise downstream clients, expanding their attack radius.

The group’s ability to evolve and integrate new attack methodologies has made it one of the most dangerous financially motivated threat actors.

The Role of Anubis Backdoor

Anubis is a stealthy backdoor malware primarily designed to maintain persistence on infected machines, collect system information, and facilitate further exploitation. Unlike the Anubis banking trojan used in Android attacks, this Windows variant focuses on espionage, privilege escalation, and command execution.

Key Capabilities of Anubis:

• Command Execution: Executes commands remotely to manipulate the infected system.
• Data Exfiltration: Steals credentials, sensitive files, and system configurations.
• Persistence Mechanisms: Establishes registry modifications and scheduled tasks to remain active.
• C2 Communication: Communicates with remote command-and-control (C2) servers for instructions.
• Credential Theft: Extracts saved credentials from browsers and password managers.
• Keylogging & Screenshot Capture: Records keystrokes and captures images of the user’s screen.

Attack Methodology

The recent FIN7 campaign utilizes compromised SharePoint sites to distribute the Anubis backdoor. The attack follows these stages:

1. Initial Access

FIN7 compromises legitimate Microsoft SharePoint servers, injecting malicious links or scripts into hosted documents. Victims unknowingly download the infected files while accessing business-related content. These compromised files may be disguised as invoices, security updates, or policy documents to increase the likelihood of successful infection.

2. Malware Deployment

Once the victim downloads and executes the payload, an obfuscated PowerShell script is triggered, downloading and installing the Anubis backdoor onto the system. The malware may be delivered in various formats, including:

• Malicious Macros: Embedded in Word or Excel documents.
• Executable Files: Disguised as legitimate software updates.
• JavaScript Loaders: Hidden within SharePoint-hosted pages.

3. Persistence Establishment

The malware establishes persistence through:

• Modifications in Windows Registry to ensure startup execution.
• Scheduled tasks that execute at system startup.
• Creation of deceptive system services mimicking legitimate processes.
• Deployment of additional scripts that maintain access in case of detection and removal.

4. Command & Control Communication

Anubis connects to FIN7-controlled C2 servers, receiving commands and transmitting stolen data. The C2 infrastructure often utilizes:

• Tor Networks: To anonymize traffic.
• Encrypted Communication: To evade detection.
• Dynamic DNS Services: For flexible domain-based operations.

5. Data Theft & Further Exploitation

FIN7 utilizes the compromised systems for:

• Credential harvesting: Extracting saved credentials from browsers and password managers.
• Network lateral movement: Exploiting Active Directory misconfigurations to infect additional devices.
• Deployment of ransomware or financial fraud schemes.

By gaining deep access into corporate networks, FIN7 can conduct large-scale financial fraud or ransom-sensitive data.

Why SharePoint?

Microsoft SharePoint is widely used for document management and collaboration, making it a valuable target for cybercriminals. Several factors contribute to its vulnerability:

• High Trust Factor: Users trust SharePoint-hosted files, reducing skepticism.
• Integration with Enterprise Systems: SharePoint is deeply integrated with Active Directory, increasing potential damage.
• Misconfigurations: Many organizations fail to properly secure SharePoint instances, leaving them exposed to attacks.

Mitigation Strategies

Organizations can take the following steps to protect against FIN7’s Anubis backdoor:

1. Strengthening SharePoint Security

• Patch SharePoint Servers: Ensure all software and SharePoint servers are up to date to prevent known exploits.
• Enforce Least Privilege Access: Restrict document editing and sharing permissions.
• Monitor File Integrity: Use file integrity monitoring (FIM) tools to detect unauthorized changes.

2. Network and Endpoint Security

• Monitor Network Traffic: Identify unusual outbound traffic that could indicate C2 communication.
• Endpoint Protection: Deploy advanced endpoint detection and response (EDR) solutions to detect anomalies.
• Restrict PowerShell Usage: Limit PowerShell execution to prevent script-based malware deployment.

3. User Awareness & Training

• Educate Employees: Train staff on the risks of downloading files from untrusted sources.
• Phishing Awareness Programs: Conduct regular phishing simulations to improve employee vigilance.
• Multi-Factor Authentication (MFA): Enforce MFA to prevent credential theft from leading to full system compromise.

The Future of FIN7’s Tactics

Given FIN7’s history, it is likely that the group will continue refining its techniques, incorporating:

• AI-Driven Malware: Leveraging AI to bypass traditional detection mechanisms.
• Cloud-Based Attacks: Exploiting cloud storage and SaaS applications for malware delivery.
• Zero-Day Exploits: Utilizing unknown vulnerabilities for initial access.

As security measures improve, cybercriminal groups like FIN7 will adopt more advanced strategies. Businesses must remain proactive in their cybersecurity approach, adopting a multi-layered defense strategy to counter evolving threats.

Conclusion

FIN7 continues to refine its attack methodologies, leveraging compromised SharePoint sites to distribute the Anubis backdoor. Organizations must stay vigilant by implementing proactive cybersecurity measures, regularly updating software, and educating employees on phishing tactics. As the threat landscape evolves, security teams must adopt a multi-layered defense strategy to mitigate risks associated with sophisticated cyber threats like FIN7.

By staying informed and implementing robust security practices, businesses can reduce the likelihood of falling victim to such targeted attacks.