750
Summary
- // if you see it open
- Kerberos v4 is obsolete and deprecated (1980s MIT work, pre-RFC 1510 / RFC 1510 era; single-DES, weak cross-realm authentication; removed from modern MIT Kerberos). Kerberos v5 uses port 88. An open 750 indicates a very old v4 KDC — a significant EOL and cryptographic-risk signal.
- // analyst note
- An open 750 indicates a very old Kerberos v4 KDC; treat as legacy and migrate to v5 (port 88) or disable.
About port 750.
Port 750/tcp is registered in the IANA Service Name and Transport Protocol Port Number Registry as rfile, a legacy remote-file service carried with no descriptive text in the registry. Port 750 was never officially assigned to Kerberos: it was reserved for the rfile and loadav services, and Kerberos v4 historically squatted on 750 as its de-facto KDC port ("kdc") before port 88 was formally assigned for Kerberos v5. The kerberos-iv ("Kerberos version IV") and loadav service names sit on 750/udp, not the TCP row — so the Kerberos association people remember is a historical, UDP-side artifact, not the current 750/tcp IANA name. The substantive analyst signal is unchanged: an open 750 points to a very old Kerberos v4 KDC, which is obsolete and deprecated (single-DES, weak cross-realm authentication; removed from modern MIT Kerberos), so it should be treated as an end-of-life, cryptographic-risk indicator and migrated to v5 (port 88) or disabled.
- IANA assignment
- 750/tcp = rfile (legacy remote-file service; no registry description) [IANA-assigned]; reference blank. Kerberos-v4 association is historical/de-facto and sits on 750/udp (kerberos-iv, loadav) — IANA Service Name and Transport Protocol Port Number Registry
- Range class
- well-known (0–1023)
- Prevalence
- very low/legacy; nmap-services de-facto low [Well-established] — nmap-services file
- Related ports
- 88 (Kerberos v5 KDC), 749 (kerberos-adm)
Primary use
IANA 750/tcp = rfile (legacy remote-file service; no registry description). Port 750 was never officially assigned to Kerberos — reserved for rfile/loadav; Kerberos v4 squatted on 750 as a de-facto KDC port before port 88 was assigned for v5
Other/unofficial uses
Kerberos v4 KDC (historical/de-facto; the kerberos-iv and loadav names are on 750/udp) [Historical]
Security implications
Kerberos v4 is obsolete/deprecated (single-DES, weak cross-realm; removed from modern MIT Kerberos); an open 750 indicates a very old v4 KDC — EOL/crypto-risk signal [Well-established]
Typically seen on
legacy Kerberos v4 KDCs
- Analyst note
- An open 750 indicates a very old Kerberos v4 KDC; treat as legacy and migrate to v5 (port 88) or disable.
Service assignments.
| Name | Protocol | Description | Open frequency |
|---|---|---|---|
| kerberos | UDP | kdc Kerberos (v4) | 0.13% |
| kerberos | TCP | kerberos-iv | 0.01% |
Service assignments from the IANA Service Name and Transport Protocol Port Number Registry, with open-frequency data from nmap-services.