Security in IT is the protection of computer systems from the theft and damage to their hardware, software or information, as well as from disruption or misdirection of the services they provide.
Also in previous versions you could define your FHIR Server to accept requests via OAuth 2.0 (e.g. for a SMART on FHIR client) but nowadays with v2024.3, which was released a while ago, there is a new feature, that enables doing this more easily - the OAuth FHIR Client QuickStart.