UAT-7237 Targets Taiwan Web Servers with Customized Open-Source Tools

The UNC5221 activity cluster, attributed to suspected Chinese hackers, has been using the BRICKSTORM malware in long-term espionage operations against U.S. organizations in the technology, legal, SaaS, and BPO sectors. The malware, a Go-based backdoor, has been active for over a year, with an average dwell time of 393 days. It has been used to steal data from various sectors, including SaaS providers and BPOs. The attackers exploit vulnerabilities in edge devices and use anti-forensics techniques to avoid detection. The malware serves multiple functions, including web server, file manipulation, dropper, SOCKS relay, and shell command execution. It targets appliances without EDR support, such as VMware vCenter/ESXi, and uses legitimate traffic to mask its C2 communications. The attackers aim to exfiltrate emails and maintain stealth through various tactics, including removing the malware post-operation to hinder forensic investigations. The attackers use a malicious Java Servlet Filter (BRICKSTEAL) on vCenter to capture credentials, and clone Windows Server VMs to extract secrets. The stolen credentials are used for lateral movement and persistence, including enabling SSH on ESXi and modifying startup scripts. The malware exfiltrates emails via Microsoft Entra ID Enterprise Apps, utilizing its SOCKS proxy to tunnel into internal systems and code repositories. UNC5221 focuses on developers, administrators, and individuals tied to China's economic and security interests. Mandiant has released a free scanner script to help defenders detect BRICKSTORM. The BRICKSTORM backdoor is under active development, with a variant featuring a delay timer for C2 communication. The attackers have exploited Ivanti Connect Secure zero-day vulnerabilities (CVE-2023-46805 and CVE-2024-21887) for initial access. The attackers have used a custom dropper to install a malicious Java Servlet filter (BRICKSTEAL) in memory, avoiding detection. The attackers have modified init.d, rc.local, or systemd files to ensure persistence on appliances. The attackers have targeted Windows environments in Europe since at least November 2022. The attackers have been linked to other related Chinese threat actors besides UNC5221. The campaign has been monitored by Mandiant since March 2025. The attackers have targeted downstream customers of compromised SaaS providers. The attackers are believed to be analyzing stolen source code to identify zero-day vulnerabilities in enterprise technologies. The attackers use a delay timer to lie dormant on infected systems until a hard-coded date. The malware employs Garble, an open-source tool, for code obfuscation to hide function names, structures, and logic. Brickstorm has been found on VMware vCenter and ESXi hosts, often deployed prior to pivoting to these systems. The attackers use legitimate cloud services like Cloudflare Workers or Heroku for C2 communications. The attackers use dynamic domains like sslip.io or nip.io that point directly to the C2 server’s IP. The attackers favor appliance and management-plane compromise, per-victim obfuscated Go binaries, delayed-start implants, and Web/DoH C2 to preserve stealth. The attackers harvest and use valid high-privilege credentials to appear as routine administrator tasks. The attackers deploy in-memory servlet filters, remove installer artifacts, and embed delayed-start logic to limit forensic traces. The attackers abuse virtualization management capabilities, such as cloning VMs to extract credential stores offline. The attackers deploy an in-memory Java Servlet filter on vCenter to intercept and decode web authentication to harvest high-privilege credentials. The attackers use a SOCKS proxy on compromised appliances to tunnel into internal networks for interactive access and file retrieval.

APT41, a China-linked threat group, has been conducting targeted phishing campaigns against U.S. trade officials, law firms, think tanks, and academic organizations. The attacks, impersonating U.S. officials and organizations, aim to steal sensitive data related to U.S.-China trade negotiations. The campaigns have been ongoing since at least January 2025, with a surge in activity observed in July and August 2025. The U.S. House Select Committee on China has issued a formal advisory warning about these activities, linking them to a Beijing-led effort to influence policy deliberations. The FBI is investigating these attacks. The phishing emails impersonate U.S. officials, including Rep. John Robert Moolenaar, and organizations such as the U.S.-China Business Council, to trick recipients into opening malicious attachments or links. The attacks exploit software and cloud services to evade detection and exfiltrate data. The goal is to gain an advantage in trade and foreign policy negotiations. The Chinese embassy has denied the allegations, stating that China opposes cyber attacks and cyber crime. APT41 has been linked to various sophisticated campaigns targeting multiple sectors, including logistics, utility companies, healthcare, high-tech, and telecommunications.

Chinese state-sponsored Advanced Persistent Threat (APT) actors, specifically the Salt Typhoon group and a newly identified group named RedNovember, have been conducting sustained campaigns to compromise critical infrastructure networks worldwide. The campaigns aim to gain long-term access to telecommunications, government, transportation, lodging, and military networks. This activity has been detailed in a joint advisory by CISA, NSA, FBI, and international partners, including Canada, Australia, New Zealand, the UK, Czech Republic, Finland, Germany, Italy, Japan, the Netherlands, Poland, and Spain. The advisory provides intelligence on tactics used by these actors and recommends mitigations to strengthen defenses. The Czech Republic's National Cyber and Information Security Agency (NUKIB) has issued a warning instructing critical infrastructure organizations to avoid using Chinese technology or transferring user data to servers located in China. The agency has re-evaluated its risk estimate of significant disruptions caused by China, now assessing it at a 'High' level. The NUKIB has confirmed malicious activities of Chinese cyber-actors targeting the Czech Republic, including a recent APT31 campaign targeting the Czech Ministry of Foreign Affairs. The advisory highlights concerns over the transfer of system and user data to China, potentially misused by state, military, or political interests. The Czech government previously accused China of targeting its critical infrastructure through APT 31, an allegation denied by the PRC but condemned by the US, EU, and NATO. The advisory suggests that individuals and organizations consider restricting or prohibiting the use of products and services that transfer data to China. The campaign has targeted at least 600 organizations across 80 countries, including 200 in the U.S. The threat actors have exploited vulnerabilities in Cisco, Ivanti, and Palo Alto Networks devices to gain initial access and have modified routers to maintain persistent access and pivot into other networks. The advisory also notes that the APT actors may target other devices such as Fortinet firewalls, Juniper firewalls, Microsoft Exchange, Nokia routers and switches, Sierra Wireless devices, Sonicwall firewalls, etc. RedNovember has targeted perimeter appliances of high-profile organizations globally, including defense and aerospace organizations, space organizations, and law firms. The group has breached at least two U.S. defense contractors, a European engine manufacturer, and a trade-focused intergovernmental cooperation body in Southeast Asia. RedNovember has used the Go-based backdoor Pantegana and Cobalt Strike as part of its intrusions, along with the Spark RAT and LESLIELOADER. The group has also used VPN services like ExpressVPN and Warp VPN to administer and connect to servers used for exploitation and communication.

Chinese hacking groups Murky Panda, Genesis Panda, and Glacial Panda have escalated their cloud and telecom espionage activities. Murky Panda, also known as Silk Typhoon, exploits trusted cloud relationships and zero-day vulnerabilities to breach enterprise networks. They target government, technology, academic, legal, and professional services entities in North America. Murky Panda exploits internet-facing appliances and known security flaws in Citrix, Commvault, and Ivanti Pulse Connect VPN to deploy web shells and custom malware. They compromise exposed SOHO devices and deploy web shells to establish persistence. In recent attacks, Murky Panda exploited zero-day vulnerabilities to break into a SaaS provider's cloud environment and gain access to the provider's application registration secret in Entra ID. They also compromised a Microsoft cloud solution provider with delegated administrative privileges (DAP) to gain Global Administrator rights across all downstream tenants. Genesis Panda, active since January 2024, targets financial, media, telecommunications, and technology sectors across 11 countries. They leverage cloud services for exfiltration and persistence. Glacial Panda targets telecoms in 12 countries, exploiting Linux systems and legacy technologies. They use privilege escalation bugs and trojanized OpenSSH components for backdoor access.

Static Tundra, a Russian state-sponsored cyber espionage group linked to the FSB's Center 16 unit, has been actively exploiting a seven-year-old vulnerability in Cisco IOS and IOS XE software (CVE-2018-0171) to gain persistent access to target networks. The group has been targeting organizations in telecommunications, higher education, manufacturing, and critical infrastructure sectors across multiple continents. The attacks involve collecting configuration files, deploying custom tools like SYNful Knock, and modifying TACACS+ configurations to achieve long-term access and information gathering. The FBI and Cisco Talos have issued advisories warning about the ongoing campaign, which has been active for over a year and has targeted critical infrastructure sectors in the US and abroad. The group has also increased attacks on Ukraine since the start of the war. The vulnerability allows unauthenticated, remote attackers to execute arbitrary code or trigger DoS conditions. Cisco has advised customers to apply the patch for CVE-2018-0171 or disable Smart Install to mitigate the risk. The group has also targeted networks of US state, local, territorial, and tribal (SLTT) government organizations and aviation entities over the last decade. The threat extends beyond Russia's operations—other state-sponsored actors are likely conducting similar network device compromise campaigns.