900

Port 900 is registered with IANA as omginitialrefs with the description "OMG Initial Refs," assignee Christian Callsen, and a blank reference field on both the TCP and UDP rows (verified against the live registry CSV). It denotes OMG (Object Management Group) Initial References, a CORBA bootstrap mechanism for resolve_initial_references that lets a CORBA client obtain initial object references — for example a handle to the Naming Service — from an Object Request Broker; it is part of the CORBA and Object Management Architecture stack of ORB, Object Services, Common Facilities, and Application Objects. The IANA reference field is blank. CORBA itself is a mature distributed-objects middleware standard whose footprint has narrowed substantially over the past two decades as REST, gRPC, and message-bus architectures displaced it, so the port is most likely to appear in legacy enterprise middleware rather than new deployments. Security-wise there is no modern protocol security profile attached to the registration, and scanner aggregators also note various de-facto uses on 900 — including some VMware Virtual Infrastructure Client or management-console setups and miscellaneous applications — which should be labeled de-facto rather than treated as the registered service. For an analyst, an open 900 usually indicates a CORBA or ORB service, and unexpected 900 should be triaged as a legacy middleware endpoint by identifying the actual listening process; nmap-services lists 900/tcp at roughly 0.000452, which is low.

IANA assignment

omginitialrefs — "OMG Initial Refs"; reference (blank); assignee Christian Callsen; dual-registered 900/tcp + 900/udp [IANA-assigned, verified live] — IANA Service Name and Transport Protocol Port Number Registry

Range class

well-known (0–1023)

Prevalence

low; nmap-services 900/tcp ~0.000452 (de-facto) [Well-established] — nmap-services file

Related ports

CORBA/IIOP-related services

Primary use

CORBA/OMG initial object-reference bootstrap (resolve_initial_references)

Other/unofficial uses

de-facto VMware VI Client / management-console and miscellaneous app uses

Security implications

no modern protocol security profile; legacy middleware exposure [Well-established]

Typically seen on

CORBA/ORB middleware services (legacy enterprise)

Analyst note

An open 900 usually indicates a CORBA/ORB service — triage unexpected 900 as legacy middleware by identifying the actual listening process; some de-facto VMware/management uses exist.