Defending Against China-Nexus Covert Networks of Compromised Devices
Defending Against China-Nexus Covert Networks of Compromised Devices
Defending against china-nexus covert networks of compromised devices executive summary Defending against China-nexus covert networks of compromised devices Explaining the widespread shift in tactics, techniques and procedures (TTPs) towards networks of compromised infrastructure, and how to defend against it Summary With support from the UK Cyber League , this advisory has been jointly released by the National Cyber Security Centre (NCSC-UK) and international partners: Australian Signals Directorate’s (ASD’s) Australian Cyber Security Centre (ACSC) Communications Security Establishment Canada’s (CSE’s) Canadian Centre for Cyber Security (Cyber Centre) Germany Federal Office for the Protection of the Constitution - Bundesamt für Verfassungsschutz (BfV) Germany Federal Intelligence Service – Bundesnachrichtendienst (BND) Germany Federal Office for Information Security - Bundesamt für Sicherheit in der Informationstechnik (BSI) Japan National Cybersecurity Office (NCO) - 国家サイバー統括室 Netherlands General Intelligence and Security Service - Algemene Inlichtingen- en Veiligheidsdienst (AIVD) Netherlands Defence Intelligence and Security Service - Militaire Inlichtingen- en Veiligheidsdienst (MIVD) New Zealand National Cyber Security Centre (NCSC-NZ) Spain National Cryptologic Centre – Centro Criptológico Nacional (CCN) Sweden National Cyber Security Centre - Nationellt cybersäkerhetscenter (NCSC-SE) United States Cybersecurity and Infrastructure Security Agency (CISA) United States Department of Defense Cyber Crime Center (DC3) United States Federal Bureau of Investigation (FBI) United States National Security Agency (NSA) Its purpose is to provide network defenders with the tools needed to defend against China-nexus cyber actors and their tactic of using large scale networks of compromised devices (covert networks) to route their cyber activity. Introduction Over the past few years there has been a major shift in the tactics, techniques and procedures (TTPs) used by China-nexus cyber actors, moving away from the use of individually procured infrastructure, and towards the use of externally provisioned, large-scale networks of compromised devices. The NCSC believes that the majority of China-nexus threat actors are using these networks (hereafter “covert networks”), that multiple covert networks have been created and are being constantly updated, and that a single covert network could be being used by multiple actors. These networks are mainly made up of compromised Small Office Home Office (SOHO) routers, as well as Internet of Things (IoT) and smart devices. Anyone who is a target of China-nexus cyber actors may be impacted by the use of covert networks. They have been used by Chinese state-sponsored actors Volt Typhoon to pre-position offensive cyber capabilities on critical national infrastructure. The group Flax Typhoon used a different covert network of compromised infrastructure to conduct cyber espionage. The use of covert networks of compromised devices - also known as botnets - to facilitate malicious cyber activity is not new, but China-nexus cyber actors are now using them strategically, and at scale. This advisory describes the typical makeup of a covert network and what they are being used for. It also includes protective advice for organizations being targeted by cyber activity using a covert network as an access vector. Covert Networks Covert networks are used to connect across the internet in a low-cost, low-risk, deniable way, disguising the origin and attribution of malicious activity. Actors have been observed using them for each phase of their Cyber Kill Chains, from performing scans as part of reconnaissance, to the delivery of malware, communicating with said malware, and exfiltrating stolen data from a victim. They can also be used for general deniable internet browsing, allowing threat actors to research exploitation techniques, new TTPs, and their victims without attribution. Some covert networks are also used by legitimate customers to browse the internet, making it challenging to attribute malicious activity. There is evidence that covert networks used by China-nexus actors are created and maintained by Chinese information security companies. A network known to network defenders as Raptor Train, which in 2024 infected more than 200,000 devices worldwide, was controlled and managed by the Chinese company, Integrity Technology Group. This company was also assessed by the FBI to be responsible for the computer intrusion activities attributed to China-based hackers known as Flax Typhoon. Botnet operations represent a significant threat to the UK by exploiting vulnerabilities in everyday internet-connected devices with the potential to carry out large-scale cyber attacks – NCSC Director of Operations, Paul Chichester Covert networks mostly consist of compromised SOHO routers, but they al