Denmark’s military intelligence agency has shut down its national cyber sensor network due to a critical security vulnerability, ending a key tool that monitored potential cyber threats across the country’s vital infrastructure.
National Surveillance Network Deemed a Risk
The Danish Defense Intelligence Service (Forsvarets Efterretningstjeneste, FE) has decided to permanently shut down the country’s centralized cyber sensor network after discovering a significant security flaw. The system had been operational since 2016 and was instrumental in providing the government with a comprehensive real-time overview of cyber activities aimed at Denmark’s critical infrastructure.
The network—used by around 300 organizations nationwide—monitored internet and server traffic within essential sectors such as energy, telecommunications, finance, health services, and transportation. It functioned as a digital web, allowing authorities to detect unusual or suspicious patterns indicative of espionage or cyberattacks. Its abrupt closure means that Denmark will no longer have the same capability for national-scale cyber surveillance.
Sensor Network Provided Centralized Threat Detection
The goal of the sensor network was to safeguard the digital backbone of Denmark. The system collected and analyzed data from strategically placed sensors within companies and institutions that form the core of the country’s critical infrastructure. These insights were funneled to national security bodies, offering a bird’s-eye view of cyber activity across different sectors.
Even though individual companies maintained their own cybersecurity systems, the central network was the only body capable of seeing the full national picture. For example, it was able to identify if traffic was communicating with known threat sources, identify coordinated attack patterns, and flag anomalies that could hint at infiltration or disruption attempts.
Though FE has assured the public that “no concrete compromises” occurred before the shutdown, the agency emphasized that continuing the use of the network presented a greater risk than taking it offline. For security reasons, the specifics of the vulnerability that led to the shutdown remain classified.
Cybersecurity Experts Describe Move as a Major Setback
Experts within the field of digital security see the shutdown as an implicit admission of a serious system flaw. Analysts note that because of the vast scope of the network, unplugging it underlines that the issue was serious enough to jeopardize national security—despite the lack of disclosed incidents.
The professor of cybersecurity at Aarhus University explained that although individual organizations can still monitor their own networks, they now lack the overarching system that can string together signals, incidents, and patterns across sectors. This makes it harder for Denmark to recognize national-level threats early.
The sensor network had already proved valuable in the past—alerting companies of emerging threats based on broader intelligence. Experts warn that its absence leaves a gap in early detection and coordinated response.”
Impact on Critical Infrastructure and Public Services
Denmark’s critical infrastructure spans 11 sectors, including energy, water supply, healthcare, emergency services, and financial systems. All these sectors had integrated into the sensor network to bolster resilience against digital threats. For instance, Copenhagen Airport—Denmark’s largest air travel hub—was among the institutions connected to the system.
Upon being notified of the shutdown, Copenhagen Airport reported that the network served as a supplementary tool to its own internal security systems and stated that the closure would have no direct impact on its operations. However, not all critical providers in Denmark operate at this level of readiness, raising concerns about inconsistent responses to potential threats moving forward.
Cyber Threat in Denmark Remains High
The closure comes at a time when the Danish Center for Cyber Security describes the cyber threat level against Denmark as “very high.” According to a 2023 threat assessment, the frequency and sophistication of attacks—ranging from ransomware to state-sponsored espionage—have surged over recent years. In 2022 alone, Denmark registered a 56% increase in cyberattacks targeting hospitals, energy providers, and public institutions.
Though authorities have not announced a direct replacement for the sensor network, the FE and the newly established Ministry for Public Security are expected to propose alternate strategies for national cybersecurity oversight. For now, the void left by the shutdown underscores how complex and fragile national cyber defense structures can be, even in technologically advanced countries such as Denmark.
