Attackers successfully breached a Polish combined heat and power (CHP) plant, disrupting its operational technology (OT) systems by leveraging a private Access Point Name (APN) to pivot from the IT network. The incident, which occurred on December 29, 2025, targeted a smaller CHP plant supplying heat to approximately 50,000 residents and was detailed in a follow-up report by Poland’s CERT. This attack vector, utilizing a private APN, is described by CERT as a novel observation in known incidents.
The intrusion began at a wind farm, where attackers exploited a Fortinet VPN and firewall device exposed to the internet. From this initial foothold, they gained access to a Teltonika cellular router, establishing an SSH tunnel to reach the private APN. This APN, managed by the distribution system operator (DSO), served as the conduit to the CHP plant’s OT network.
Once inside the CHP plant’s network, the attackers identified a Wago PLC and used its SSH access to further penetrate the operational environment. Following approximately a week of reconnaissance, they connected to Siemens PLCs, switching them to a stop mode and setting a password that locked out operators. This action prevented legitimate personnel from altering the controllers' state or control logic.
The physical impact of the attack manifested in the shutdown of the steam turbine and water treatment system, disrupting the cogeneration process and causing a temporary loss of service continuity. Although plant staff quickly restored the affected systems, preventing a heat or electricity outage, the incident highlighted the critical vulnerability.
In an attempt to conceal their tracks, the attackers damaged the Wago controller that had served as a gateway, corrupting its partition table. A subsequent factory reset by the affected entity failed to repair the partition table, rendering the device inoperable and preventing the recovery of valuable logs during the investigation.
The incident also revealed the complexity of real-world intrusions into control environments. Attackers reconfigured Moxa serial device servers and network switches to block legitimate access and made attempts to interact with ABB and Schneider Electric variable frequency drives, though some of these efforts were only partially successful or failed.
A key architectural detail was that the DSO required all communication between its ICT network and the remote terminal unit (RTU) to occur over a serial protocol, specifically DNP3.0. While the compromised facility used a Teltonika RUTX50 router to meet this requirement, no protocols were in place for managing the cellular router’s administrative interface. This oversight allowed the router, configured with both a serial link to the RTU and an Ethernet interface connected to a VLAN managed by the compromised central firewall, to become a critical pivot point.
The attackers did not rely on sophisticated zero-day exploits. Instead, they leveraged an accessible edge device, an existing private APN in the communication path, and weak or exposed access points, demonstrating patience in their progression from reconnaissance to disruption. CERT noted that this type of private APN setup is not uncommon, underscoring the broader relevance of the findings beyond Poland.
Initially, the facility attributed the process interruption to an error by contractor engineers during maintenance work. However, CERT Polska, aware of similar events, initiated an incident handling process, which confirmed the cyberattack hypothesis.
In early 2026, cybersecurity researchers linked a late-2025 cyberattack on Poland’s energy system to the Russia-linked Sandworm APT group. While this attribution was made with medium confidence based on malware analysis and observed tactics, techniques, and procedures, no successful disruption was confirmed in the broader energy sector attacks. The DynoWiper, a destructive wiper malware, was identified in an attempted cyberattack against Poland’s energy sector on December 29, 2025, though its architecture was noted to be clearly destructive.
