Largest Multi-Agency Cyber Operation Mounted to Counter Threat Posed by Advanced Persistent Threat (APT) Actor UNC3886 to Singapore’s Telecommunications Sector

1. The Cyber Security Agency of Singapore (CSA) and the Infocomm Media Development Authority (IMDA) shared details of a multi-agency cybersecurity operation, codenamed Operation CYBER GUARDIAN, to defend our telecommunications sector.

Background

2. On 18 July 2025, Coordinating Minister for National Security Mr K Shanmugam shared that Advanced Persistent Threat (APT) actor UNC3886 had been detected attacking our critical infrastructure. No further details were shared then, to preserve operational security. Over the past months, our investigations have indicated that UNC3886 had launched a deliberate, targeted, and well-planned campaign against Singapore’s telecommunications sector. All four of Singapore’s major telecommunications operators (“telcos”) – M1, SIMBA Telecom, Singtel and StarHub – have been the target of attacks.

Singapore’s telcos targets of cyberattacks

3. APTs are sophisticated and persistent, getting past defences with advanced methods over time. UNC3886 is an APT actor with deep capabilities. UNC3886 deployed advanced tools in their campaign to gain access into our telco systems. For example:

• In one instance, they used a zero-day exploit¹ to bypass a perimeter firewall of our telcos and gained access into our telco networks. They also managed to exfiltrate a small amount of technical data; this is believed to be primarily network-related data to advance the threat actors’ operational objectives.
• In another instance, the threat actor utilised advanced tools and techniques such as rootkits² to maintain persistent access and cover their tracks and evade detection. This made it challenging for cyber defenders to detect their presence, requiring the cyber defenders to conduct comprehensive security checks across the networks.

Operation CYBER GUARDIAN mitigated serious threat posed by UNC3886

4. The threat actor’s activities were initially detected by the telcos, who then notified IMDA and CSA of the breach. CSA, IMDA and other government agencies swiftly launched a coordinated whole-of-Government response, in partnership with the telcos to contain the breach. The operation, codenamed Operation CYBER GUARDIAN, is Singapore’s largest coordinated cyber incident response effort undertaken to date, spanning more than eleven months. Over 100 cyber defenders across agencies such as CSA, IMDA, the Centre for Strategic Infocomm Technologies (CSIT), the Digital and Intelligence Service (DIS), the Government Technology Agency of Singapore (GovTech) and the Internal Security Department (ISD) were involved in the operation.

5. Under Operation CYBER GUARDIAN, the authorities worked closely with the telcos to limit UNC3886’s movement into the networks and ensure our systems remain safe to use. So far, the attack by UNC3886 has not resulted in the same extent of damage as cyberattacks elsewhere.

• The threat actor was able to gain unauthorised access into some parts of telco networks and systems. In one instance, they were able to gain limited access to critical systems but did not get far enough to have been able to disrupt services.
• There is no evidence to-date that sensitive or personal data such as customer records were accessed or exfiltrated.
• There is also no evidence that the threat actor managed to disrupt telecommunications services such as internet availability.

6. Cyber defenders have since implemented remediation measures, closed off UNC3886’s access points and expanded monitoring capabilities in the targeted telcos.

7. The close partnership between the public and private sector in Operation CYBER GUARDIAN reflects our national doctrine of cyber defence, in which government agencies, as well as the private sector come together to collectively defend our cyber space. The doctrine also guides capability development across our cyber ecosystem, sets out the roles that different parties should play in cyber defence, and the actions that should be taken during a cyber incident. This coordinated approach is a key pillar of Singapore’s cyber security.

The fight is ongoing

8. While our collective efforts have contributed to containing the attacks so far, we must be prepared that there may be future attempts to gain access into our telco infrastructure. Telcos are strategic targets for threat actors, including state-sponsored ones. They play a foundational role in powering the digital economy and transmit vast amounts of information, including sensitive data. If threat actors succeed in attacking our telcos, they have the potential to undermine our national security and our economy.

9. The Government takes a serious view of the cyberattack against our telcos. CSA and IMDA have been working closely with our telcos to strengthen their cyber defences, enhance detection capabilities, and deploy active monitoring systems to maintain vigilance against new attempts by UNC3886 to re-enter their networks. Telcos have also been putting in place interventions including joint threat hunting, penetration testing, and levelling up of capabilities. CSA will also be progressively introducing initiatives to raise the level of capabilities across our cyber ecosystem, to enable better and more timely responses against cyber threats and to strengthen Singapore’s cyber defences.

10. Speaking at an engagement event for cyber defenders involved in Operation CYBER GUARDIAN, Minister for Digital Development and Information and Minister-in-charge of Cybersecurity & Smart Nation Group, Josephine Teo, thanked the defenders for their contributions and called for continued vigilance.

11. In her address, she also highlighted the important role played by critical infrastructure operators who are at the frontlines of the battle against cyber threat actors. She said, “Your actions, or inaction, can determine whether we succeed or fail in protecting our critical infrastructure, and our national security. I urge all of you to continue investing in upgrading your systems as well as your capabilities”. In closing, Minister Teo acknowledged the need for the government and critical infrastructure owners to work together as a team, so that we can be effective against sophisticated adversaries and protect everything we care about.