olemus
sõltub kontekstist

näiteid
ISO 7498, 17090, 21091, 22600, 24534, ISO/TS 19299:
avatud süsteemi kihi teenus, mis tagab süsteemide või andmeedastuste adekvaatse turvalisuse
= service, provided by a layer of communicating open systems, which ensures adequate security of the systems or of data transfers

ülevaateid
https://en.wikipedia.org/wiki/Security_service_(telecommunication)

http://www.idc-online.com/technical_references/pdfs/data_communications/Security_Services.pdf

https://nvlpubs.nist.gov/nistpubs/legacy/sp/nistspecialpublication800-35.pdf