Poland’s computer emergency response team (CERT) has published a report detailing the recent attack by Russia-linked hackers on the country’s power grid.
The attack targeted communication and control systems at roughly 30 sites, including combined heat and power (CHP) plants and renewable energy dispatch centers for wind and solar facilities.
The hackers gained access to industrial control systems (ICS), but primarily targeted grid safety and stability monitoring systems rather than active power generation systems. While some ICS devices were permanently damaged, the incident did not result in any electrical outages.
“It should be noted, however, that given the level of access obtained by the attacker, there was a risk of causing a disruption in electricity generation at the affected facilities,” CERT.PL said in its report. “Even if such a disruption had occurred, analyses indicate that the combined loss of capacity across all 30 facilities would not have affected the stability of the Polish power system during the period in question.”
According to the Polish CERT, the attack began as early as March 2025, with reconnaissance, unauthorized data access, and credential-harvesting attempts detected through July.
The CERT reported that each of the targeted facilities had Fortinet FortiGate devices exposed to the internet, using default credentials and lacking multi-factor authentication. These Fortinet appliances, which served as both firewalls and VPN interfaces, represented the initial attack vector.
The hackers initiated disruptive and destructive actions on December 29, with some of the activity partially automated.
Targeted ICS
CERT Polska’s report identifies three ICS vendors whose products were targeted in the attack: Hitachi Energy, Moxa, and Mikronika.
In the case of Hitachi, targeted devices included RTU560 remote terminal units (RTUs), which threat actors accessed using default credentials. The access allowed the attackers to upload malicious firmware. Investigators found that a security feature meant to prevent malicious firmware updates had not been enabled, but even if it had been enabled the devices were affected by CVE-2024-2617, a known flaw allowing unsigned firmware updates.
The threat actors also targeted Hitachi Relion protection and control relays. Access to these devices was possible due to the failure to disable a default FTP account (the vendor recommends disabling this account) and the use of default credentials.
The Russia-linked hackers also targeted RTUs and human-machine interfaces (HMIs) made by Mikronika, a Poland-based industrial automation solutions firm. Both types of ICS devices were protected with default credentials, allowing attackers to make malicious changes that ultimately enabled them to initiate destructive actions.
The threat actors deployed wipers on Windows machines hosting the HMI software, which, on devices protected by default local admin credentials, caused damage.
Moxa NPort serial device servers were also targeted. According to CERT.PL, the attackers used exposed web interfaces and default credentials to access the systems and then reset them to factory settings, changed their login password, and assigned IP addresses that prevented legitimate users from accessing them.
“In each of the analyzed cases, all Moxa devices accessible at the facility were targeted,” CERT.PL explained.
Industrial cybersecurity firm Dragos previously reported that RTUs were ultimately recovered, but some unspecified ICS devices were damaged beyond repair.
While some threat actors have advanced capabilities and significant resources for conducting ICS attacks, this incident once again shows that industrial systems are often easy to hack even for low-skilled hackers.
ICS vendors respond
Hitachi Energy published an advisory on Friday to inform customers that its RTU560 and Relion 650 products were targeted in the attack on Poland’s energy grid.
The vendor has urged customers to update their devices and implement general cybersecurity measures, but noted that the attackers hacked its devices due to “insufficient cyber-hygiene within the broader system environment”.
Hitachi noted that the compromised devices were configured with default credentials, had recommended security features disabled, were running outdated firmware, and were behind vulnerable firewalls.
Mikronika told SecurityWeek that it collaborated with CERT Polska in investigating the incident and actively participated in the analysis of the entire attack.
The company’s CSO, Tomasz Szała, confirmed to SecurityWeek that there is no evidence that zero-day vulnerabilities were used in the attack. “The attackers only leveraged default credentials,” Szała noted.
At the time of writing Moxa has not published an advisory and it has not responded to SecurityWeek’s request for comment.
Attribution
Polish officials blamed Russia for the cyberattack shortly after the incident became public. However, cybersecurity firm ESET was the first to attribute it to a specific threat actor.
ESET reported with medium confidence, based on its analysis of the malware and associated TTPs, that the APT named Sandworm was behind the attack. The company’s analysis has focused on the wiper malware used in the attack, including DynoWiper.
Dragos attributed the attack — also with moderate confidence — to a group it tracks as Electrum, which it describes as related to but not always identical to Sandworm.
Sandworm has been tied to Russian military intelligence and is mainly known for its destructive attacks, including the 2016 Ukraine power grid attack.
In contrast, CERT.PL has connected the attack to a threat actor tracked as Static Tundra, Berserk Bear, Ghost Blizzard, and Dragonfly, which focuses on reconnaissance and espionage.
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