The tornado alert system was switched on at around 9 p.m. for three minutes. An hour later, a second alert was issued, this time for roughly 30 minutes. Authorities were prompted that the system was used illegally and tried to shut it down electronically. Since they could not override the hacker, the system had to be disconnected from the power grid. These incidents outline the importance of securing key infrastructures against unauthorized use of the system. The systems are activated via a radio signal that contains a unique code. Since the investigation did not yield any signs of system malfunction, one of the most plausible explanations is that someone copied this code.”]