major threat to security
as defined in Commission Decision (EU, Euratom) 2015/443 of 13 March 2015 on Security in the…, Article 1, point (17) (Definitions)
a threat to security that can reasonably be expected to lead to loss of life, serious injury or harm, significant damage to property, compromise of highly sensitive information, disruption of IT systems or of essential operational capacities of the Commission;