243
Summary
- // if you see it open
- No CVE or named malware family is tied specifically to port 243. A third-party port-lookup page (auditmypc.com) carries generic templated trojan/virus warning text also present across many of its other port pages, but that same page's own structured data field reports 'No' for virus/trojan association — so this is not recorded as a substantiated finding.
- // analyst note
- sparse, undated legacy System Port with no confirmed software behind it — an open port 243 in the wild would be unusual and worth investigating rather than assuming benign.
About port 243/tcp.
Port 243/tcp is registered with IANA under the service name sur-meas, described as "Survey Measurement," with assignee and contact listed as Dave Clark (MIT LCS). The assignment is dual-registered — the identical service name, description, and assignee appear on both 243/tcp and 243/udp in the IANA Service Name and Transport Protocol Port Number Registry. The registry entry carries no RFC or other reference document, and no registration or modification date is listed; this is consistent with many legacy System Port assignments from the pre-RFC-tracking era of the registry, and the blank fields are reported here as blank rather than filled with an invented RFC number or date. Beyond the bare registry listing, there is little independent evidence of the assignment's real-world history or use. No credible documentation of any software product, protocol specification, or service that actually implements "Survey Measurement" on this port was found in this research pass, and no exposure-scanning writeups, CVEs, or malware families are tied specifically to port 243. One third-party port-lookup site (auditmypc.com) carries generic templated warning language about trojans/viruses that appears across many of its port pages regardless of actual risk, and that same page's own structured data field reports "No" for virus/trojan association with this port — so the boilerplate text should not be read as a substantiated finding. Given the sparse footprint, port 243 should be treated as an obscure, rarely (if ever) deployed legacy assignment rather than a service analysts are likely to encounter live.
- IANA assignment
sur-meas— "Survey Measurement"; reference (blank — no RFC cited in IANA registry); assignee/contact Dave Clark (MIT LCS); dual-registered 243/tcp + 243/udp [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=243- Range class
- well-known (0–1023) [Confirmed]
- Registration/modification date
- not listed in the IANA registry (undated legacy System Port assignment) [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.txt
- Prevalence
- no scanning-campaign or exposure statistics specific to this port were found in this pass [Unknown]
- Related ports
- no directly related-port cluster identified for this obscure legacy assignment [Unknown]
Primary use
no independently documented software or protocol implementing "Survey Measurement" was found; the registry entry appears to be an assignee reservation without a public specification [Unknown]
Other/unofficial uses
none found [Unknown]
Security implications
no CVE or named malware family tied specifically to port 243; a third-party page's generic trojan-warning boilerplate is contradicted by that same page's own "No" data field, so it is not recorded as a genuine association
Typically seen on
no current or historical deployments documented; treat an open port 243 as an anomaly rather than an expected service [Unknown]
- Analyst note
- sparse, undated legacy System Port with no confirmed software behind it — an open port 243 in the wild would be unusual and worth investigating rather than assuming benign.
About port 243/udp.
Port 243/udp is registered with IANA under the service name sur-meas, described simply as "Survey Measurement." The registration is dual: the same name, description, and contact appear for both 243/tcp and 243/udp in the IANA Service Name and Transport Protocol Port Number Registry, with no RFC or other document cited in the Reference column — that field is blank in the source, not merely undocumented on a mirror. The assignee and contact are listed as "Dave_Clark," notable because a Dave Clark (MIT) was an influential figure in early ARPANET/Internet architecture during the era many of these low three-digit ports were registered, though the registry entry itself gives no further identifying detail or protocol specification tying the assignment to that history beyond the name. No protocol document, daemon, or piece of software implementing "sur-meas" could be found in this research pass — there is no public RFC, no vendor implementation, and no CVE or malware family associated with the port. Generic community port-list mirrors (SpeedGuide, T1 Shopper, and similar) repeat the bare IANA description without adding usage detail, and one broad community Shodan-style scan-port gist includes 243 in an undifferentiated sweep list with no port-specific finding. Practically, this port has no documented modern use and should be treated as a legacy, effectively dormant IANA assignment; any live traffic on 243/udp merits investigation as anomalous rather than expected service traffic.
- IANA assignment
sur-meas— "Survey Measurement"; reference (blank — no RFC cited in registry); assignee/contact Dave_Clark; dual-registered 243/tcp + 243/udp [Confirmed] — local cached IANA Service Name and Transport Protocol Port Number Registry (the IANA Service Name and Transport Protocol Port Number Registry, row 556 udp / row 555 tcp) and https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=243- Range class
- well-known (0–1023) [Confirmed] — port number falls in the IANA well-known range
- Registration/modification dates
- not recorded in the IANA registry (columns blank) [Confirmed — absence confirmed, not merely unresearched] — local IANA CSV
- Related ports
- the same-era small-numbered "sur-*"/measurement-adjacent legacy IANA assignments in the low 200s range; no confirmed functional relationship established [Unknown]
Primary use
no documented modern protocol usage found; legacy registration with no accompanying specification [Unknown] — https://www.speedguide.net/port.php?port=243, http://www.t1shopper.com/tools/port-number/243/, https://www.tecniwao.com/en/puerto/udp/243/
Common software/implementations
none identified
Security implications
no CVE, malware family, or documented backdoor use found; appears only in a generic, undifferentiated community port-sweep list alongside hundreds of other ports [Likely — absence of evidence, single low-signal source] — https://gist.github.com/s0md3v/3e953e8e15afebc1879a2245e74fc90f
Typically seen on
no live-host prevalence data available for this research pass [Unknown]
- Analyst note
- treat any observed 243/udp traffic as anomalous — there is no legitimate modern service expected to use this port.
Service assignments.
| Name | Protocol | Description | Open frequency |
|---|---|---|---|
| sur-meas | UDP | Survey Measurement | 0.05% |
| sur-meas | TCP | Survey Measurement | 0.00% |
Service assignments from the IANA Service Name and Transport Protocol Port Number Registry, with open-frequency data from nmap-services.