266

Port 266/tcp is registered with IANA under the service name sst, with the description "SCSI on ST." The assignment is dual-registered — the same service name, description, and assignee appear on both the TCP and UDP rows of the IANA Service Name and Transport Protocol Port Number Registry — and the assignee/contact is listed as Donald D. Woelz. The registry's Reference, Registration Date, and Modification Date fields are all blank for this entry, which is typical of assignments made in the registry's earliest era, before IANA began systematically recording those columns; no RFC or other standards document backs the assignment. The literal meaning of "SCSI on ST" is not spelled out anywhere in the registry or in any RFC, and no deployed daemon, client, or product implementing a SCSI-over-TCP/UDP protocol on port 266 could be identified in general web or vendor documentation — the most plausible reading is a proprietary or research-project transport for SCSI commands over a serial/tape ("ST") link, but that reading is inference, not a sourced fact. Port 266 does not appear in Wikipedia's curated list of well-known TCP/UDP ports, consistent with it being an obscure, likely-dormant reservation rather than an actively deployed or commonly scanned service; no security advisories, malware associations, or exposure-scanning statistics specific to this port were found.

IANA assignment

sst — "SCSI on ST"; assignee/contact Donald D. Woelz; dual-registered 266/tcp + 266/udp [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv

IANA Reference field

blank — no RFC or standards document cited for this assignment [Confirmed, absence-of-data] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv

Registration Date / Modification Date

blank in the registry; left null rather than invented (no epoch placeholder assigned) [Confirmed, absence-of-data] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv

Range class

well-known (0–1023) [Confirmed]

Security implications / exposure-scanning data

no authoritative source found describing scanning activity or vulnerabilities specific to port 266 [Unknown]

Literal protocol meaning ("SCSI on ST" — presumed SCSI commands carried over a serial/tape transport)

not documented anywhere found [Unknown]

Known software/daemons implementing this service

none identified in web search [Unknown]

Presence in curated port references

absent from Wikipedia's "List of TCP and UDP port numbers" [Likely, absence-of-evidence for prevalence] — https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers

Port 266/udp is registered with IANA under the service name sst, described simply as "SCSI on ST," with Donald D. Woelz listed as both assignee and contact of record. The registry entry is dual: the identical service name, description, and contact appear on 266/tcp as well, meaning both transports were assigned together rather than the UDP side being registered independently later. No RFC or other reference document is cited for this entry, and the Registration Date and Modification Date fields in IANA's own CSV export are blank — a common state for old, pre-tracking-era assignments rather than a data gap on our end. What "SCSI on ST" actually names in technical terms is not documented anywhere IANA publishes; it reads as a scheme for carrying SCSI commands over some transport abbreviated "ST," but no primary source spells out the wire format, and no currently maintained software, vendor product, or public implementation surfaced in a search. Nothing ties the port to malware, backdoors, or notable scanning activity either — it is simply too obscure to have generated documented incident history. Two secondary port-database sites (SpeedGuide, tcp-udp-ports.com) returned HTTP 403 and could not be checked. Treat 266/udp as a legacy, effectively unused IANA registration: legitimate in the registry, but with no evidence of real-world deployment.

IANA assignment

sst — "SCSI on ST"; reference (blank — no RFC cited); assignee/contact Donald D. Woelz; dual-registered 266/tcp + 266/udp [Confirmed] — IANA Service Name and Transport Protocol Port Number Registry (https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv; also https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?page=6, and the local cached copy at the IANA Service Name and Transport Protocol Port Number Registry)

Range class

well-known (0–1023) [Confirmed]

Registration/modification dates

blank in the IANA registry itself — left blank, not fabricated [Confirmed] — same IANA CSV citation

Prevalence

no nmap-services or scan-frequency data for this port was located in this pass [Unknown]

Related ports

266/tcp — identical dual registration (same service name, description, and contact) [Confirmed]

Primary use

registered name for "SCSI on ST" — likely a scheme for transporting SCSI commands over a network transport abbreviated "ST"; no published spec or RFC describes the wire protocol, and the etymology of "ST" is unconfirmed by any primary source

Other/unofficial uses

none found — no currently maintained software, vendor, or product implementing this service was located in this pass [Unknown]

Security implications

no malware, trojan, backdoor, or exploit associations found for port 266 in a targeted search; two secondary port-lookup sites (SpeedGuide.net, tcp-udp-ports.com) returned HTTP 403 and could not be used as sources [Unknown] — checked https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers (port 266 is not listed there; table skips from 264 to 280)

Typically seen on

no data located [Unknown]

Analyst note

Port 266/udp has no confirmed modern software, deployment, or threat association in available sources; treat an observed instance as an obscure legacy registration rather than a normal or inherently suspicious service without further context.