373
Summary
- // typical exposure
- Anomalous (rarely legitimately open) — This is a legacy 1990s IANA registration naming a company (Legent Corporation) that has not existed since its 1995 acquisition by CA, with no assignee/contact on record, no published protocol, and no documented modern software use, so a live listener is unexpected and should be investigated rather than treated as routine.
- // analyst note
- A responsive port 373 has no known legitimate modern use — the company named in the registry (Legent Corporation) has not existed since its 1995 acquisition by CA, no assignee or contact is on record, and no protocol spec was ever published. Treat as anomalous and investigate.
- // if you see it open
- No published protocol spec exists for legent-1, so behavior of any live listener cannot be assessed from documentation. SANS ISC reports a 'green' (low) threat level with only sporadic, low-volume scanning and no logged CVEs or malware/trojan association as of 2026-07-27. Legent Corporation, the company named in the registry, has not existed since its 1995 acquisition by CA, and no assignee or contact is on record, so a responsive port 373 today has no known legitimate modern use and is anomalous.
About port 373/tcp.
Port 373/tcp carries legent-1, a legacy IANA registration with no documented protocol or active software tied to it today; it should not be exposed to the public internet and a live listener here is worth investigating rather than trusting as a normal service.
The IANA Service Name and Transport Protocol Port Number Registry lists 373 as legent-1, with description "Legent Corporation" but no assignee or contact on record — an unusual gap for a named corporate registration — and a blank Reference column, meaning no RFC or protocol specification was ever published for it. The same name is dual-registered on 373/udp.
Legent Corporation was a mainframe and network/systems-management software vendor active in the 1990s; it was acquired by Computer Associates (CA) in 1995. No contemporary vendor documentation, forum post, or community port-lookup source was found describing a currently-running application that uses this port, so the protocol's actual on-wire behavior is Unknown.
SANS Internet Storm Center shows port 373 at a low ("green") threat level as of 2026-07-27, with only sporadic, low-volume scanning traffic and no logged CVEs or malware/trojan association.
- IANA assignment
legent-1— description "Legent Corporation"; assignee and contact not recorded (both columns blank); reference blank; dual-registered 373/tcp + 373/udp [Confirmed] — IANA Service Name and Transport Protocol Port Number Registry- Range class
- well-known (0–1023)
- Prevalence
- not established — no nmap-services open-frequency figure surfaced in research [Unknown]
- Related ports
- no verified cluster of related Legent-registered ports was found in this research
Primary use
Unknown — no RFC or protocol spec was ever published; historically tied to Legent Corporation, a mainframe/systems-management software vendor acquired by Computer Associates (CA) in 1995
Other/unofficial uses
none documented; no modern software or community sighting found using this port [Unknown]
Security implications
SANS ISC "green" (low) threat level, sporadic low-volume scanning, no CVEs, no malware/trojan association as of 2026-07-27
Typically seen on
legacy/decommissioned Legent Corporation software (pre-1995) if anywhere; otherwise anomalous since the company no longer exists [Unknown]
- Analyst note
- A responsive port 373 has no known legitimate modern use — the company named in the registry (Legent Corporation) has not existed since its 1995 acquisition by CA, no assignee or contact is on record, and no protocol spec was ever published. Treat as anomalous and investigate.
About port 373/udp.
Port 373/udp is IANA-registered under the name legent-1, with description "Legent Corporation" but no assignee or contact on record; no confirmed modern service or protocol specification exists for it, so a live host on 373/udp should be treated as unexpected rather than something intentionally exposed to the public internet.
The IANA registry lists the description as "Legent Corporation" with no assignee, no contact, and no reference RFC recorded — an unusual gap for a named corporate registration. Both 373/tcp and 373/udp are dual-registered to the same name, a common pattern from that era of the port registry when a company reserved a number without publishing a formal protocol document.
Legent Corporation was a mainframe and systems-management software vendor active in the late 1980s and 1990s; it was acquired by Computer Associates in 1995 (consistent with the repo's 373/tcp, 374/tcp, and 374/udp sibling entries). No publicly documented protocol, product, or ongoing service tied to port 373 has been located, and no CVE or malware family is associated with it.
Because the registration predates modern web-searchable documentation and Legent no longer exists as an independent company, community port databases (SpeedGuide, AdminSub) could not be checked this pass — HTTP 403 and HTTP 522 respectively; those remain open follow-ups for a future pass.
- IANA assignment
legent-1— "Legent Corporation"; reference (blank); assignee not recorded; dual-registered 373/tcp + 373/udp [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry-740; IANA Service Name and Transport Protocol Port Number Registry- Range class
- well-known (0–1023) [Confirmed]
- Prevalence
- nmap-services observed open-frequency 373/udp ≈ 0.000395 — very low (roughly 4 in 10,000 scanned hosts in the nmap-services sample) [Likely] — nmap-services dataset
- Related ports
- 373/tcp (dual-registered legent-1) [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry
Primary use
Unknown — no documented protocol specification or RFC exists for the legent-1 registration [Unknown]
Other/unofficial uses
Unknown — no community-sourced software sightings could be verified this pass (SpeedGuide/AdminSub fetches returned HTTP 403 / 522) [Unknown]
Security implications
No CVE or malware association documented; the registration reads as an orphaned legacy assignment (Legent Corp acquired by Computer Associates in 1995)
Typically seen on
Unknown — no confirmed deployments located [Unknown]
- Analyst note
- A responsive 373/udp has no known legitimate modern use; treat as anomalous and investigate rather than assume normal service traffic.
Service assignments.
| Name | Protocol | Description | Open frequency |
|---|---|---|---|
| legent-1 | UDP | Legent Corporation (now Computer Associates Intl.) | 0.04% |
| legent-1 | TCP | Legent Corporation (now Computer Associates Intl.) | 0.00% |
Service assignments from the IANA Service Name and Transport Protocol Port Number Registry, with open-frequency data from nmap-services.