k4spreader (Dropper) – Malware

Overview

The rapid evolution of cyber threats continues to challenge cybersecurity professionals worldwide, with malware tools becoming increasingly sophisticated and elusive. One such emerging threat is k4spreader, a new malware tool developed by the notorious “8220” mining gang. This Chinese cybercriminal group, also known as “Water Sigbin,” has been active since 2017, initially gaining infamy for leveraging zero-day vulnerabilities to deploy mining trojans on compromised servers. In June 2024, a new variant of their toolkit—named k4spreader—was identified, showcasing their continued innovation in the realm of malicious software.

k4spreader represents a significant advancement in the gang’s arsenal, acting as a comprehensive installer designed to deploy and manage other forms of malware. Written in CGO mode and utilizing a combination of C and Go programming languages, k4spreader’s primary functions include system persistence, self-update capabilities, and the installation of additional malicious payloads such as the Tsunami DDoS botnet and the PwnRig mining program. The tool is notable for its use of multiple layers of packing to evade detection and its ability to perform various system modifications to ensure persistence and functionality.

The development of k4spreader highlights the gang’s shift from simple mining operations to more complex and multifaceted cybercriminal activities. By incorporating features like disabling firewalls, cleaning up competing malicious processes, and dynamically downloading and executing further payloads, k4spreader exemplifies the evolving strategies used by cybercriminal groups to maintain control over compromised systems. Its sophisticated design not only aids in the execution of DDoS attacks and mining operations but also reflects a broader trend towards more resilient and adaptable malware.

Targets

Information

How they operate

Infiltration and Initial Access

The initial stage of k4spreader’s operation involves exploiting vulnerabilities in public-facing applications. Leveraging techniques such as Exploit Public-Facing Application (T1190), the malware targets flaws in web services or applications accessible over the internet. This approach enables k4spreader to gain unauthorized access to systems, often bypassing conventional security measures. Once inside the network, k4spreader deploys its payload using Command and Scripting Interpreter (T1059) techniques, executing malicious scripts or commands to facilitate further actions. Additionally, Dynamic Link Library Injection (T1055) may be used to inject malicious code into legitimate processes, allowing the malware to evade detection and maintain a stealthy presence.

Persistence and Privilege Escalation

To ensure it remains active and undetected, k4spreader employs persistence mechanisms. By creating or modifying registry keys and startup folders, the malware ensures that it is executed upon system boot or user logon, utilizing techniques like Registry Run Keys / Startup Folder (T1060) and Boot or Logon Autostart Execution (T1547). Furthermore, k4spreader may escalate its privileges through Exploitation of Vulnerability (T1203), exploiting system weaknesses to gain higher-level access. This elevation of privileges is crucial for executing more advanced commands and accessing sensitive data.

Defense Evasion and Credential Access

In its quest to evade detection, k4spreader utilizes obfuscation techniques to conceal its activities. Obfuscated Files or Information (T1027) are employed to hide the malware’s presence from security tools, while Disabling Security Tools (T1089) techniques may be used to interfere with antivirus programs and firewalls. Additionally, k4spreader might engage in Credential Dumping (T1003), extracting and collecting credentials from compromised systems. This capability allows it to perform lateral movements within the network and access additional resources, further enhancing its reach and impact.

Discovery and Lateral Movement

The malware conducts System Information Discovery (T1082) to gather details about the infected system’s hardware, software, and network configuration. This information is essential for optimizing its operations and identifying potential targets within the network. k4spreader may also employ Remote Desktop Protocol (T1076) to facilitate lateral movement, using compromised systems as stepping stones to spread across the network.

Data Collection and Exfiltration

In the final stages of its operation, k4spreader focuses on collecting valuable data. It uses techniques such as Data from Information Repositories (T1213) to gather information from databases, file shares, or other repositories. For exfiltration, the malware utilizes Exfiltration Over Command and Control Channel (T1041), sending collected data through encrypted communication channels to avoid detection. If combined with ransomware functionalities, k4spreader may also engage in Data Encrypted for Impact (T1486), encrypting files on the infected systems to demand ransom payments.

MITRE Tactics and Techniques

Initial Access (TA0001)

Exploit Public-Facing Application (T1190): k4spreader may exploit vulnerabilities in public-facing applications to gain initial access to a target system. This is often achieved through vulnerabilities in web services or applications that are exposed to the internet.

Execution (TA0002)

Command and Scripting Interpreter (T1059): k4spreader may utilize command-line interfaces or scripting languages to execute malicious commands or scripts. This technique is commonly used to deploy additional payloads or perform system modifications.
Dynamic Link Library Injection (T1055): This technique involves injecting malicious code into legitimate processes, allowing the malware to evade detection and gain persistence.

Persistence (TA0003)

Registry Run Keys / Startup Folder (T1060): k4spreader may create or modify registry keys or startup folders to ensure it is executed each time the system starts.
Boot or Logon Autostart Execution (T1547): The malware can configure itself to run automatically at system boot or user logon, ensuring it maintains persistence on the infected machine.

Privilege Escalation (TA0004)

Exploitation of Vulnerability (T1203): k4spreader might exploit known vulnerabilities to escalate privileges on the target system, gaining higher-level access to facilitate its operations.

Defense Evasion (TA0005)

Obfuscated Files or Information (T1027): k4spreader employs various obfuscation techniques to hide its presence from security tools and analysts. This includes packing or encrypting its payloads to evade detection.
Disabling Security Tools (T1089): The malware may attempt to disable or interfere with security measures such as firewalls or antivirus software to avoid detection and removal.

Credential Access (TA0006)

Credential Dumping (T1003): k4spreader might include functionality to extract and collect credentials from compromised systems, potentially for further exploitation or lateral movement.

Discovery (TA0007)

System Information Discovery (T1082): The malware may gather information about the system’s configuration, including hardware, software, and network details, to optimize its activities and identify additional targets.

Lateral Movement (TA0008)

Remote Desktop Protocol (T1076): k4spreader might use protocols like RDP to move laterally across a network, leveraging compromised systems to spread further.

Collection (TA0009)

Data from Information Repositories (T1213): The malware may collect data from various repositories, such as databases or file shares, to exfiltrate valuable information from the target network.

Exfiltration (TA0010)

Exfiltration Over Command and Control Channel (T1041): k4spreader might exfiltrate data over its command and control channels, using encrypted communication to avoid detection.

Impact (TA0040)

Data Encrypted for Impact (T1486): If combined with ransomware components, k4spreader could encrypt data on infected systems to cause disruption and demand a ransom.

References

• 8220 Mining Gang’s New Tool: k4spreader