This report finds that the trend to digitization, when combined with a lack of executive-level awareness of the risks involved, means that nuclear plant personnel may not realize the full extent of their cyber vulnerability and are thus inadequately prepared to deal with potential attacks. Specific findings include the following: The conventional belief that all nuclear facilities are "air gapped" (isolated from the public Internet) is a myth. The commercial benefits of Internet connectivity means that a number of nuclear facilities now have VPN connections installed, which facility operators are sometimes unaware of. Search engines can readily identify critical infrastructure components with such connections. Even where facilities are air gapped, this safeguard can be breached with nothing more than a flash drive. Supply chain vulnerabilities mean that equipment used at a nuclear facility risks compromise at any stage. A lack of training, combined with communication breakdowns between engineers and security personnel, means that nuclear plant personnel often lack an understanding of key cyber security procedures. Reactive rather than proactive approaches to cyber security contribute to the possibility that a nuclear facility might not know of a cyber attack until it is already substantially underway. In the light of these risks, the report outlines a blend of policy and technical measures that will be required to counter the threats and meet the challenges.