361

Port 361/tcp is IANA-registered under the service name semantix, but no RFC, protocol specification, or vendor documentation describes what it actually does — with no confirmed legitimate service behind the registration, traffic on this port has no established reason to be exposed to the public internet and should be treated as anomalous until explained locally.

The IANA registry entry lists 361 as dual-registered for TCP and UDP, with assignee "[Semantix]" and a blank Reference column (no RFC cited), and no registration or modification date recorded. Beyond this bare listing, IANA supplies no description of the protocol's purpose, origin, or intended use.

A third-party aggregator (portsmaster.net) claims port 361 is used for OLSR mesh-routing traffic, but this conflicts with both the IANA registry entry and with OLSR's own documented port (UDP/698 per RFC 3626), so the claim was investigated and rejected rather than folded into this entry as fact.

SANS Internet Storm Center rates port 361 "green" — its lowest, minimal-threat band — as of 2026-07-25, showing only low, single-digit-count background-scan source IPs and listing no CVE and no malware association for the port. That is the same per-port-number reading that applies to the 361/udp registration.

IANA assignment

semantix — "Semantix"; reference (blank — no RFC cited); assignee [Semantix]; dual-registered 361/tcp + 361/udp [Confirmed] — IANA Service Name and Transport Protocol Port Number Registry

Range class

well-known (0–1023) [Confirmed]

Prevalence

not established; no nmap-services open-frequency figure exists for this port [Unknown]

Related ports

361/udp (same semantix dual registration); 698/udp (OLSR's actual protocol port, unrelated to 361 despite the rejected third-party claim) [Confirmed] — IANA registry, RFC 3626

Primary use

Unknown — IANA lists only the bare service name with no protocol description, spec, or vendor documentation identifying the function

Other/unofficial uses

none credibly verified; a third-party claim of OLSR mesh routing was investigated and rejected as contradicting both the IANA registry and OLSR's actual documented port (UDP/698)

Security implications

SANS ISC rates port 361 "green" (low/minimal threat) as of 2026-07-25, with low single-digit-count background-scan source IPs and no CVE or malware association listed; because no confirmed service function exists, an open 361/tcp should be treated as anomalous pending local investigation

Typically seen on

no confirmed host population or software; the traffic SANS ISC observes is consistent with routine internet background scanning rather than an active service

Analyst note

An open port 361 has a documented IANA name but no documented protocol behind it — investigate locally rather than assuming a known service, and disregard unverified third-party "OLSR" attributions.

Port 361/udp is registered with IANA under the service name "semantix," but no protocol specification, software vendor, or documented function could be confirmed for it — with no verified legitimate use, this port has no confirmed reason to be exposed to the public internet.

IANA's registry lists 361 as dual-registered on TCP and UDP under the name "semantix," with the Reference field blank — no RFC or defining specification is cited. This is consistent with an old, sparsely documented registration rather than an actively maintained protocol entry.

A low-quality aggregator search result claimed port 361 is used by OLSR (Optimized Link State Routing), but this appears to be an error: OLSR's actual assigned port is 698/udp, not 361, and no primary source ties OLSR to 361. That claim is rejected rather than reported as fact.

A secondary source described a 2023-11-16 de-assignment date for the semantix entry, but this is confirmed incorrect: the primary IANA registry lists 361/tcp and 361/udp as active assignments — service name "semantix," description "Semantix," assignee/contact [Semantix] — with Registration Date, Modification Date, Reference, and Assignment Notes all blank. There is no de-assignment of port 361. The 2023-11-16 de-assignment date belongs to port 359 (Description "Reserved," Modification Date 2023-11-16, Assignment Notes "De-Assigned on 2023-11-16"); the secondary source appears to have conflated 359 with 361 — a second miscitation trap alongside the OLSR mix-up above.

No credible community-sourced sighting of specific software using 361/udp was found; aggregator port-lookup pages simply mirror the bare IANA label without naming real applications. SANS Internet Storm Center rates the port "green" (low/minimal threat), with only routine background-scan traffic and no CVE or malware association.

IANA assignment

semantix — description "Semantix"; assignee/contact [Semantix]; Registration Date, Modification Date, Reference, and Assignment Notes all blank; dual-registered 361/tcp + 361/udp, both active [Confirmed] — IANA Service Name and Transport Protocol Port Number Registry

Range class

well-known (0–1023)

Prevalence

not established in this research pass [Unknown]

Related ports

698/udp (OLSR — commonly confused with 361 in low-quality sources, but a distinct IANA assignment)

Primary use

Unknown — IANA lists only the bare service name "semantix" for TCP/UDP port 361; no protocol specification, vendor, or description text beyond "Semantix" could be located in this research pass

Other/unofficial uses

none credibly found; a search-aggregator claim tying this port to OLSR (Optimized Link State Routing) is rejected as a likely error since OLSR's actual assigned port is 698/udp [Unknown]

Security implications

SANS ISC rates 361/udp "green" (low/minimal scanning threat) as of 2026-07-25, with low single-digit-count background-noise source IPs and no CVE or malware association listed

Typically seen on

no confirmed legitimate deployment; traffic observed is consistent with routine internet background scanning rather than an active service

Analyst note

361/udp has no documented function in the IANA registry beyond the bare name "semantix." Traffic on this port lacks a confirmed legitimate explanation and should be treated as anomalous or scanning noise pending further evidence; do not assume it is a live, exposed service. Port 361 is NOT de-assigned — the registry shows it active with no dates recorded; a 2023-11-16 de-assignment date circulating in a secondary source actually belongs to the unrelated port 359.