LockBit 4.0 Leak Exposes Disorganized Ransomware Ecosystem

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.

The RaccoonO365 phishing network, a financially motivated threat group, was disrupted by Microsoft's Digital Crimes Unit (DCU) and Cloudflare. The operation, executed through a court order in the Southern District of New York, seized 338 domains used by the group since July 2024. The network targeted over 2,300 organizations in 94 countries, including at least 20 U.S. healthcare entities, and stole over 5,000 Microsoft 365 credentials. The RaccoonO365 network operated as a phishing-as-a-service (PhaaS) toolkit, marketed to cybercriminals via a subscription model on a private Telegram channel. The group used legitimate tools like Cloudflare Turnstile and Workers scripts to protect their phishing pages, making detection more challenging. The mastermind behind RaccoonO365 is believed to be Joshua Ogundipe, who received over $100,000 in cryptocurrency payments. The group is also suspected to collaborate with Russian-speaking cybercriminals. Cloudflare executed a three-day 'rugpull' against RaccoonO365, banning all identified domains, placing interstitial 'phish warning' pages, terminating associated Workers scripts, and suspending user accounts to prevent re-registration.

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.

A supply chain attack involving multiple npm packages with over 2.6 billion weekly downloads has been discovered. The attack, which began in April 2025, involved the injection of malicious code into npm packages after compromising a maintainer's account via a phishing attack. The malicious code targets cryptocurrency wallets, including Atomic and Exodus, and redirects transactions to addresses controlled by threat actors. The attack has now expanded to include additional maintainers and packages, further broadening its impact. The attack impacted roughly 10% of all cloud environments, but the attackers made little profit. The malicious packages were removed within two hours of the attack, and the injected code targeted browser environments, hooking Ethereum and Solana signing requests. The attack was discovered and mitigated quickly, preventing more severe security incidents. The attack follows a series of similar incidents targeting JavaScript libraries, emphasizing the ongoing threat to the npm ecosystem and the broader supply chain. The compromised packages include popular ones such as ansi-regex, ansi-styles, chalk, debug, and others, collectively attracting over 2 billion weekly downloads. The malicious code operates by intercepting network traffic and application APIs, targeting various cryptocurrencies including Ethereum, Bitcoin, Solana, Tron, Litecoin, and Bitcoin Cash.

A zero-day vulnerability in WhatsApp (CVE-2025-55177) was exploited in targeted attacks against specific users, chained with a separate iOS flaw (CVE-2025-43300). The flaw allowed unauthorized users to trigger content processing from arbitrary URLs on targeted devices. Apple issued threat notifications to users targeted in mercenary spyware attacks, which included individuals based on their status or function, such as journalists, lawyers, activists, politicians, and senior officials. The attacks highlight the risks of chaining multiple vulnerabilities to compromise targets, emphasizing the need for comprehensive security measures. WhatsApp patched the issue and notified affected users. Apple has sent threat notifications multiple times a year since 2021, alerting users in over 150 countries, including a fourth campaign in France in 2025. The attacks began with the exploitation of the WhatsApp zero-day vulnerability, which was chained with an iOS flaw in sophisticated attacks. Apple has been issuing threat notifications to users targeted in these attacks, advising them to enable Lockdown Mode and seek emergency security assistance. Apple introduced Memory Integrity Enforcement (MIE) in the latest iPhone models to combat memory corruption vulnerabilities, and the number of U.S. investors in spyware and surveillance technologies has increased significantly.