Malware Persistence Techniques and Defense Strategies

A new variant of the XCSSET macOS malware has been detected, targeting Xcode developers with enhanced features. This variant includes improved browser targeting, clipboard hijacking, and persistence mechanisms. The malware spreads by infecting Xcode projects, stealing cryptocurrency, and browser data from infected devices. The malware uses run-only compiled AppleScripts for stealthy execution and employs sophisticated encryption and obfuscation techniques. It incorporates new modules for data exfiltration, persistence, and clipboard monitoring. The malware has been observed in limited attacks, with Microsoft sharing findings with Apple and GitHub to mitigate the threat. Developers are advised to keep macOS and apps up to date and inspect Xcode projects before building them.

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.

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 medium-severity vulnerabilities in Supermicro Baseboard Management Controller (BMC) firmware allow attackers to bypass firmware verification and update the system with malicious firmware. These vulnerabilities, CVE-2025-7937 and CVE-2025-6198, exploit flaws in the cryptographic signature verification process. The vulnerabilities affect the Root of Trust (RoT) security feature, potentially allowing attackers to gain persistent control over the BMC system and the main server OS. The issues were discovered by Binarly, a firmware security company. Supermicro has released firmware fixes for impacted models, and Binarly has released proof-of-concept exploits for both vulnerabilities. CVE-2025-7937 is a bypass for a previously disclosed vulnerability, CVE-2024-10237, which was reported by NVIDIA. CVE-2025-6198 bypasses the BMC RoT security feature, raising concerns about the reuse of cryptographic signing keys.

The ShadowV2 botnet targets misconfigured Docker containers on Amazon Web Services (AWS) to deploy a Go-based malware, turning infected systems into nodes for a distributed denial-of-service (DDoS) botnet. This botnet is available for rent to conduct DDoS attacks, employing advanced techniques such as HTTP/2 Rapid Reset and bypassing Cloudflare's Under Attack mode. The botnet was detected on June 24, 2025, and is believed to be part of a DDoS-for-Hire service. The botnet uses a Python-based C2 framework hosted on GitHub Codespaces and a Go-based remote access trojan (RAT) for command execution and communication. The malware first spawns a generic setup container from an Ubuntu image, installs necessary tools, and then builds and deploys a live container. This approach may help avoid leaving forensic artifacts on the victim machine. The malware communicates with a C2 server to receive commands and conduct attacks. The botnet's dynamic container deployment allows highly configurable attacks while concealing activity behind cloud-native architecture. The botnet targets 24,000 IP addresses with port 2375 open, though not all are exploitable. The malware sends a heartbeat signal to the C2 server every second and polls for new attack commands every five seconds. The botnet is actively used, with observed commands to launch attacks against at least one website.