EggStreme Fileless Malware Used in Philippine Military Breach

The Cybersecurity and Infrastructure Security Agency (CISA) issued Emergency Directive 25-03, mandating federal agencies to identify and mitigate zero-day vulnerabilities in Cisco Adaptive Security Appliances (ASA) exploited by an advanced threat actor. The directive requires agencies to account for all affected devices, collect forensic data, and upgrade or disconnect end-of-support devices by September 26, 2025. The vulnerabilities allow threat actors to maintain persistence and gain network access. Cisco identified multiple zero-day vulnerabilities (CVE-2025-20333, CVE-2025-20362, CVE-2025-20363, and CVE-2025-20352) in Cisco ASA, Firewall Threat Defense (FTD) software, and Cisco IOS software. These vulnerabilities enable unauthenticated remote code execution, unauthorized access, and denial of service (DoS) attacks. GreyNoise detected large-scale campaigns targeting ASA login portals and Cisco IOS Telnet/SSH services, indicating potential exploitation of these vulnerabilities. The campaign is widespread and involves exploiting zero-day vulnerabilities to gain unauthenticated remote code execution on ASAs, as well as manipulating read-only memory (ROM) to persist through reboot and system upgrade. CISA and Cisco linked these ongoing attacks to the ArcaneDoor campaign, which exploited two other ASA and FTD zero-days (CVE-2024-20353 and CVE-2024-20359) to breach government networks worldwide since November 2023. CISA ordered agencies to identify all Cisco ASA and Firepower appliances on their networks, disconnect all compromised devices from the network, and patch those that show no signs of malicious activity by 12 PM EDT on September 26. CISA also ordered that agencies must permanently disconnect ASA devices that are reaching the end of support by September 30 from their networks. The U.K. National Cyber Security Centre (NCSC) confirmed that threat actors exploited the recently disclosed security flaws in Cisco firewalls to deliver previously undocumented malware families like RayInitiator and LINE VIPER. Cisco began investigating attacks on multiple government agencies in May 2025, linked to the state-sponsored ArcaneDoor campaign. The attacks targeted Cisco ASA 5500-X Series devices to implant malware, execute commands, and potentially exfiltrate data. The threat actor modified ROMMON to facilitate persistence across reboots and software upgrades. The compromised devices include ASA 5500-X Series models running specific software releases with VPN web services enabled. The Canadian Centre for Cyber Security urged organizations to update to a fixed version of Cisco ASA and FTD products to counter the threat. Nearly 50,000 Cisco ASA and FTD appliances are vulnerable to actively exploited flaws. The vulnerabilities CVE-2025-20333 and CVE-2025-20362 enable arbitrary code execution and access to restricted URL endpoints. The Shadowserver Foundation discovered over 48,800 internet-exposed ASA and FTD instances still vulnerable to the flaws. The majority of vulnerable devices are located in the United States, followed by the United Kingdom, Japan, Germany, Russia, Canada, and Denmark. The Shadowserver Foundation's data is as of September 29, indicating a lack of response to the ongoing exploitation activity. Greynoise had warned on September 4 about suspicious scans targeting Cisco ASA devices, indicating upcoming undocumented flaws. CISA's emergency directive gave 24 hours to FCEB agencies to identify and upgrade vulnerable Cisco ASA and FTD instances. CISA advised that ASA devices reaching their end of support should be disconnected from federal networks by the end of September. The U.K. NCSC reported that the hackers deployed Line Viper shellcode loader malware and RayInitiator GRUB bootkit.

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.

Two malware strains were discovered in an organization's network after attackers exploited two zero-day vulnerabilities in Ivanti Endpoint Manager Mobile (EPMM). The vulnerabilities, CVE-2025-4427 and CVE-2025-4428, allow for authentication bypass and remote code execution, respectively. Attackers used these flaws to gain access to the EPMM server, execute arbitrary code, and maintain persistence. The attack began around May 15, 2025, following the publication of a proof-of-concept exploit. The malware sets include loaders that enable arbitrary code execution and data exfiltration. The vulnerabilities affect Ivanti EPMM development branches 11.12.0.4, 12.3.0.1, 12.4.0.1, and 12.5.0.0 and their earlier releases. A China-nexus espionage group was leveraging the vulnerabilities since at least May 15, 2025. The threat actor targeted the /mifs/rs/api/v2/ endpoint with HTTP GET requests and used the ?format= parameter to send malicious remote commands. The malware sets include distinct loaders with the same name, and malicious listeners that allow injecting and running arbitrary code on the compromised system. The threat actor delivered the malware through separate HTTP GET requests in segmented, Base64-encoded chunks. Organizations are advised to update their EPMM instances, monitor for suspicious activity, and implement access restrictions to prevent unauthorized access to mobile device management systems.

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 phishing campaign targeting KazMunayGas employees was initially attributed to the Noisy Bear threat actor. The activity, codenamed Operation BarrelFire, involved phishing emails with malicious attachments designed to deliver a reverse shell. However, KazMunayGas clarified that the campaign was a planned phishing test conducted in May 2025. The campaign utilized a compromised email address from KazMunayGas's finance department to send phishing emails containing a ZIP attachment with a Windows shortcut (LNK) downloader, a decoy document, and a README.txt file. The payloads included a batch script and a PowerShell loader named DOWNSHELL, culminating in the deployment of a DLL-based implant. The infrastructure was hosted on the Russia-based bulletproof hosting service Aeza Group, which was sanctioned by the U.S. in July 2025. The campaign was initially linked to a new threat group tracked by Seqrite Labs as Noisy Bear, active since at least April 2025. Seqrite Labs disputed KazMunayGas's claim that the attack was a security exercise, citing forensic clues and infrastructure overlaps with other Central Asian attacks. The threat activity has geopolitical implications, targeting a state-owned oil and gas company in Kazakhstan, which is a significant player in Europe's energy market.