Summary
APT41, also known as Brass Typhoon, Wicked Panda, and Winnti, a Chinese state-sponsored threat actor, has been linked to a sophisticated cyber campaign targeting the gambling and gaming industry, according to a new report from security company Security Joes.
Over at least six months, APT41 shifted from traditional espionage to financially motivated attacks, using techniques like Phantom DLL Hijacking and WMIC.exe abuse for persistence and evasion. They further deployed sophisticated malware to establish communication with Command-and-Control (C2) servers, allowing them to profile infected systems and target machines within specific VPN subnets for further exploitation. APT41 adapted their tools and tactics based on the security team’s responses, maintaining persistent access to the compromised network for nearly nine months.
The attack overlaps with a similar intrusion campaign dubbed Operation Crimson Palace. While the initial access method is unknown, spear-phishing is a likely vector. Once inside, APT41 executed a DCSync attack to steal password hashes of service and admin accounts, gaining deeper access and persistence, seeking administrative and developer accounts.
APT41’s actions resulted in data exfiltration, financial losses, potential cryptocurrency mining, operational disruption, and reputational damage for the targeted gambling and gaming industry organizations.
Recommendations
To mitigate the risks posed by advanced threat actors like APT41, the following recommendations should be implemented, focusing on prevention, detection, and response for RH-ISAC Core Members:
Strengthen Perimeter and Access Controls
- Multi-Factor Authentication (MFA): Implement MFA for all user accounts, especially those with administrative and privileged access. This can reduce the effectiveness of credential theft through phishing or DCSync attacks.
- Network Segmentation: Separate critical infrastructure, such as VPN subnets (e.g., the targeted 10.20.22 subnet), from the general network. Isolating high-value systems helps minimize the impact of lateral movement.
- Least Privilege Access: Apply the principle of least privilege to all accounts, restricting access rights to only those necessary for specific roles. This limits the damage caused by compromised accounts.
- Monitor VPN Access: Pay special attention to VPN connections, as APT41 targeted VPN subnets. Ensure proper logging and monitoring of VPN traffic for anomalous activities.
Enhance Monitoring and Threat Detection
- Behavioral Analytics and Threat Hunting: Implement User and Entity Behavior Analytics (UEBA) to detect unusual patterns in user behavior, such as suspicious use of admin credentials or unusual command executions (e.g., WMIC abuse).
- Monitor Living Off the Land (LOLBIN) Activity: Continuously monitor the usage of legitimate binaries like WMIC.exe, PowerShell, and others commonly abused in LOLBIN attacks. Any unauthorized or anomalous use should be investigated.
- Advanced Endpoint Detection and Response (EDR): Deploy advanced EDR solutions that can detect stealthy malware, memory attacks, and fileless threats. Ensure real-time monitoring of endpoint activities to catch DCSync attacks, DLL hijacking, and credential theft attempts.
- Track Indicators of Compromise (IoCs): Actively monitor for IoCs such as malicious files (TSVIPSrv.dll, texttable.xsl), suspicious domains (e.g., time.qnapntp[.]com), and GitHub scraping activities. Use threat intelligence feeds to update detection rules regularly.
Improve Incident Response Capabilities
- Conduct Regular Threat Simulations: Perform red team exercises or simulated cyberattacks (including phishing) to assess your organization’s readiness to respond to advanced persistent threats (APTs) like APT41. Improve your incident response playbooks based on findings.
- Immediate Credential Revocation: In the event of a compromise, revoke the credentials of compromised accounts, especially administrative and service accounts, to prevent attackers from maintaining persistence.
- Segregate Response Teams from Regular IT: Attackers like APT41 are known to watch defender movements. Have segregated response teams with separate access, and avoid making remediation actions visible to attackers. Covertly reset credentials and isolate affected systems.
Deploy Robust Phishing Defenses
- Email Filtering and Anti-Phishing Measures: Deploy robust email filtering solutions to detect and block spear-phishing attempts. Scan attachments and links for malicious content, and implement sandboxing to analyze suspicious emails.
- User Awareness Training: Continuously train employees to recognize phishing emails and suspicious content, especially targeting those with access to critical systems (administrators, developers). Conduct regular phishing awareness drills.
Harden Systems Against DLL Hijacking and Script Execution
- DLL Hijacking Protection: Implement controls to prevent DLL hijacking by ensuring all system and application DLLs are loaded from known, trusted directories. Use endpoint protection tools that can monitor and block unauthorized DLL loading.
- Script Execution Restrictions: Limit the execution of scripts, especially from tools like exe, PowerShell, or cmdexe. Implement application whitelisting, ensuring only authorized scripts and binaries are allowed to run.
- Disable or Monitor WMIC: Disable WMIC on systems where it is not needed, or closely monitor its usage, as it was a key tool abused by APT41 in this attack.
