X.500

X.500 is the ITU-T family of standards for directory services, of which the most widely used derivative is LDAP (Lightweight Directory Access Protocol). X.509 certificates take their distinguished-name format from the X.500 information model. Pure X.500 directories are rare in modern deployments, but the underlying concepts remain foundational to identity systems.

Categories: Identity and SubscriberSecurity ControlsProtocols and Standards

X.500 in context

Subscriber identifiers (IMSI, SUPI, MSISDN, IMEI) anchor authentication, charging and lawful interception. Any protocol that leaks a permanent identifier is treated as a privacy defect, which is why 5G introduced SUCI concealment on the air interface.

Security controls span signaling firewalls (SS7/Diameter/GTP screening), transport encryption (IPsec, TLS, PRINS), identity and access on OSS/BSS, and monitoring at both packet and log level. Controls are audited against GSMA FS.11/FS.19/FS.20/FS.36.

To place X.500 in the wider telecom-security picture, review OASIS, IMSI Catcher (Cell Site Simulator), Key Management, SCADA, USIM and SM-DP+: each entry cross-references back to this page so you can walk the topic in either direction.

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