Law enforcement authorities in Spain arrested two former employees for conducting a cyberattack against the country’s radioactivity alert network.

Two individuals were detained in Spain for disabling over a third of the sensors that make up the country’s radioactivity alert network (RAR). The network monitors radiation levels to inform the population in case of a nuclear accident.

The attack was carried out in March and June last year, with perpetrators disabling over 300 out of 800 radiation sensors. Some of the affected devices were responsible for monitoring radiation levels around the country’s nuclear power plants.

According to Spanish Police, the attackers first breached systems operated by the General Directorate of Civil Protection and Emergencies (DGPGE), a government body responsible for RAR operations and maintenance.

Once inside, the attackers tried to delete the RAR management web application in the control centre. The second part of the attack was aimed at disabling the radiation sensors.

After a year-long investigation, authorities discovered that the attackers were employees of a DGPGE contracted company responsible for RAR system maintenance.