This code system http://hl7.org/fhir/security-source-type defines the following codes:

CodeDisplayDefinition
1User DeviceEnd-user display device, diagnostic device.
2Data InterfaceData acquisition device or instrument.
3Web ServerWeb Server process or thread.
4Application ServerApplication Server process or thread.
5Database ServerDatabase Server process or thread.
6Security ServerSecurity server, e.g. a domain controller.
7Network DeviceISO level 1-3 network component.
8Network RouterISO level 4-6 operating software.
9Otherother kind of device (defined by DICOM, but some other code/system can be used).