Discovering Splinter: A New Post-Exploitation Red Team Tool in the Cybersecurity Arsenal

In the ever-evolving world of cybersecurity, new tools and techniques are continually emerging-some designed to fortify defenses, while others are created to exploit vulnerabilities. Recently, Palo Alto Networks uncovered a new post-exploitation red team tool named “Splinter.” Found during routine memory scanning, this tool has sparked interest in the cybersecurity community. While such tools are often used for legitimate red team exercises, in the wrong hands, they can be weaponized by malicious actors, highlighting the importance of understanding and addressing the threats they pose.

Understanding Splinter: A Post-Exploitation Tool

According to Palo Alto Networks: Splinter is a powerful, custom-built post-exploitation tool developed using the Rust programming language, known for its focus on performance and memory safety. It was discovered by Palo Alto Networks’ Advanced WildFire memory scanning tools during an incident response engagement, and further analysis revealed that several other systems had been affected by the same tool.

Post-exploitation tools like Splinter are typically used after initial access to a system has been gained. They enable attackers to maintain persistence, execute commands, and steal data from compromised systems. These tools are widely utilized in red team exercises, where penetration testers simulate real-world attacks to test the security of an organization. However, when they fall into the hands of cybercriminals, the consequences can be severe.

Technical Insights Into Splinter
“Splinter is developed in Rust, a relatively new programming language that’s recommended for developing memory-safe software. However, it has densely layered runtime code, which amounts for up to 99% of a program’s code. This density makes analysis a real challenge for malware reverse engineers.” Splinter operates by using a modular task-based framework. It communicates with a command-and-control (C2) server, allowing attackers to issue commands and retrieve data from infected machines. Some of Splinter’s capabilities include:

1. Command Execution: Splinter can remotely execute Windows commands on the victim’s system.
2. File Transfer: It can upload or download files between the compromised machine and the attacker’s C2 server.
3. Process Injection: The tool supports remote process injection, allowing it to load malicious code into another process to avoid detection.
4. Self-Deletion: Once the attacker has completed their tasks, Splinter can self-delete, erasing its traces from the infected system.

Interestingly, Splinter was found to be developed in Rust, a language increasingly popular for its efficiency and security. Rust’s dense runtime code makes the tool more challenging to analyze for reverse engineers. The large file sizes, stemming from the inclusion of numerous external libraries (known as “crates” in Rust), contribute to the tool’s complexity.

One notable observation is Splinter’s use of HTTPS encryption for all network communications, ensuring that its data transfers between the victim’s system and the C2 server are difficult to intercept or analyze. While Splinter is not as well-known or sophisticated as Cobalt Strike, another widely used red team tool, its capabilities are still robust and potentially dangerous if used maliciously.

10 Best Practices to Protect Against Post-Exploitation Tools Like Splinter

1. Regularly Update Systems: Ensure that all operating systems and software are regularly updated to patch vulnerabilities that can be exploited by tools like Splinter.
2. Deploy Endpoint Detection and Response (EDR): Use EDR solutions to monitor systems for suspicious behavior, such as process injections and unauthorized file transfers.
3. Monitor Network Traffic: Implement network monitoring tools to detect abnormal traffic, such as encrypted connections to unfamiliar IP addresses or C2 servers.
4. Implement Least Privilege: Limit user permissions and only provide administrative access to individuals who absolutely need it. This reduces the potential damage if an account is compromised.
5. Multi-Factor Authentication (MFA): Use MFA across all systems and services, especially for sensitive or administrative accounts, to prevent unauthorized access.
6. Conduct Regular Penetration Testing: Regular red team exercises and penetration tests can help organizations identify vulnerabilities before attackers exploit them.
7. Isolate Critical Systems: Segment your network to limit access to critical systems. This can contain a breach and prevent attackers from moving laterally across the network.
8. Utilize Application Whitelisting: Prevent unauthorized or unknown applications from executing on systems by implementing application whitelisting policies.
9. Log and Audit Activity: Regularly audit system logs and activity to detect unusual behavior, such as new services starting unexpectedly or spikes in network traffic.
10. Employee Security Training: Educate employees on phishing, spear-phishing, and other social engineering tactics that attackers use to gain initial access to a system.

Conclusion:
Splinter’s discovery is a reminder of the ever-evolving cyber threat landscape, particularly when it comes to post-exploitation tools. While tools like Splinter are intended for legitimate use in red team exercises, their misuse by cybercriminals can result in severe security breaches. As organizations continue to adapt their defenses, they must remain vigilant against new tools and techniques. By implementing the best practices outlined above, organizations can significantly reduce the risks posed by post-exploitation frameworks like Splinter and fortify their security posture. “Cortex XDR and XSIAM help detect and block known samples, and Behavioral Threat Protection monitors for post-exploitation activity.” “Palo Alto Networks has shared these findings with our fellow Cyber Threat Alliance (CTA) members. CTA members use this intelligence to rapidly deploy protections to their customers and to systematically disrupt malicious cyber actors. Learn more about the Cyber Threat Alliance.”. “If you think you might have been compromised or have an urgent matter, contact the Unit 42 Incident Response team“

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