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) are the anchor for authentication, charging, lawful interception and fraud analytics. Any protocol or interface that leaks a permanent identifier is treated as a serious privacy defect, which is why 5G introduced SUCI concealment on the air interface.

Security controls in telecom span signaling firewalls (SS7/Diameter/GTP screening at the network edge), transport encryption (IPsec, TLS, PRINS), identity and access on OSS/BSS, and monitoring at both the packet and log level. Controls are audited against GSMA FS.11/FS.19/FS.20/FS.36 and, in Europe, NIS2 sectoral rules.

To place X.500 in the wider telecom-security picture, review OASIS, IMSI Catcher (Cell Site Simulator), Key Management, SCADA, USIM and SM-DP+.

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