"The Industrial Control Systems Cyber Emergency Response Team (ICS-CERT) provides guidance to critical infrastructure asset owners to assist in preparing their networks to handle and analyze a cyber incident. Even the best cyber defense mechanisms cannot prevent all cyber incidents. The sheer volume of intrusions attempted against information technology systems every day creates the possibility that a cyber attack could penetrate the numerous defensive systems in place on many networks. In order to provide the swiftest incident response and recovery possible, preparation and planning are essential."
Industrial Control Systems Cyber Emergency Response Team (ICS-CERT): https://ics-cert.us-cert.gov/