312
Summary
- // typical exposure
- Anomalous (rarely legitimately open) — The vslmp registration is undocumented and essentially never observed open in real-world scans, matching the Anomalous profile of legacy, rarely-legitimate ports rather than a designed-for-internet or routinely-restricted service.
- // analyst note
- An open port 312 is statistically rare and carries no confirmed legitimate current use beyond a decades-old individual IANA registration and a dated Apple Xsan association — investigate rather than assume routine service.
- // if you see it open
- No CVEs or notable exploit/scanning-campaign activity found specific to this port. The underlying vslmp protocol is undocumented (acronym not expanded in any verifiable source), so its behavior cannot be assessed. If open, may reflect legacy macOS Xsan (SAN) administration traffic, which should be confined to trusted internal storage networks. Essentially never legitimately open in current deployments; an open 312 is anomalous and worth investigating.
About port 312/tcp.
Port 312/tcp carries no service with confirmed active deployment today; IANA reserves it under the name vslmp, but the registration is decades old, undocumented beyond the bare acronym, and essentially never observed open in real-world scans — so it should not be trusted as legitimate infrastructure and an open 312/tcp warrants investigation rather than routine acceptance.
IANA's Service Name and Transport Protocol Port Number Registry lists 312 as vslmp, description "VSLMP," dual-registered for both tcp and udp, assigned to an individual (Gerben Wierda) with no RFC or other reference document cited and no registration date shown — typical of a pre-2001-era assignment. This is the authoritative record of what the number is officially reserved for.
The acronym VSLMP is not expanded anywhere in the IANA record itself, and automated searches produced three mutually inconsistent, unsourced guesses at what it might stand for. None could be verified against a primary source, so no expansion is reported here — an honest Unknown rather than a fabricated definition.
Separate from the IANA registration, Wikipedia's port list documents an unofficial, vendor-specific reuse: 312/tcp for macOS Xsan administration, Apple's storage-area-network filesystem management feature. Xsan is a legacy, niche enterprise product Apple has since moved away from, so this association is itself dated.
No currently maintained, widely-deployed software is documented as actively using port 312. Nmap's scan-frequency telemetry (nmap-services) shows the port among the least commonly seen open ports in its default-scan corpus, and no CVEs or notable scanning-campaign activity specific to this port turned up in this pass.
- IANA assignment
vslmp— description "VSLMP"; assignee/contact[Gerben_Wierda]; reference blank; dual-registered 312/tcp + 312/udp [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry (IANA snapshot); https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=vslmp- Range class
- well-known (0–1023)
- Prevalence
- nmap-services open-frequency ≈0.000000 (312/tcp), ≈0.000593 (312/udp) — among the least-observed open ports in the corpus [Likely] — https://svn.nmap.org/nmap/nmap-services
- Related ports
- no specific documented relation; comparable in profile to other rarely-used legacy registrations (e.g. 1/tcp
tcpmux)
Primary use
Unknown — IANA lists only the bare acronym "VSLMP" with no protocol specification, RFC, or expansion verifiable from primary sources
Other/unofficial uses
unofficial/vendor reuse for macOS Xsan (Apple SAN filesystem) administration
Security implications
no CVEs or notable exploit/scanning-campaign activity found specific to this port; legacy/dormant registration with no confirmed current mainstream software
Typically seen on
essentially never open; if observed, may reflect legacy macOS Xsan SAN-administration traffic or represent an anomaly
- Analyst note
- An open port 312 is statistically rare and carries no confirmed legitimate current use beyond a decades-old individual IANA registration and a dated Apple Xsan association — investigate rather than assume routine service.
About port 312/udp.
Port 312/udp carries no confirmed application-layer service; IANA's Service Names and Transport Protocol Port Number Registry lists it only as vslmp, with a description field that is just the bare acronym "VSLMP" and no protocol specification, so it should be treated as an unconfirmed, rarely-seen legacy assignment rather than something with an established role on the public internet.
The IANA record assigns 312/udp to Gerben_Wierda as both assignee and contact, and pairs it with an identical 312/tcp registration under the same service name and assignee. The Registration Date, Modification Date, and Reference fields are all blank in the registry — this is recorded as Unknown rather than a fabricated date or RFC citation.
A commonly repeated expansion, "Virtual Software Library Master Password protocol," appears on secondary port-lookup sites and in a Cisco NBAR protocol-pack index, but it is not present in the IANA record itself and could not be confirmed against a primary document during this research pass, so it is tagged as an unverified community gloss rather than a confirmed fact.
Real-world usage is negligible: the nmap-services frequency database lists 312/udp at roughly 0.06% of scanned hosts historically, versus effectively zero for 312/tcp, and no vendor software was confirmed to actually bind to this port in either direction.
- IANA assignment
vslmp— description field is the bare acronym "VSLMP" (no expansion given); assignee/contact Gerben_Wierda; reference blank; dual-registered 312/tcp + 312/udp with identical fields [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry#L636, https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv- Range class
- well-known (0–1023)
- Registration/modification dates
- blank in the IANA registry — recorded as Unknown, not fabricated [Confirmed (confirmed absent)] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv
- Prevalence
- nmap-services open-frequency 312/udp ≈ 0.000593 (rare); 312/tcp ≈ 0.000000 (negligible) [Likely, dated secondary source] — https://svn.nmap.org/nmap/nmap-services
- Related ports
- 312/tcp (dual-registered, identical vslmp assignment) [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry#L635
Primary use
Unknown — no protocol specification or vendor documentation confirms what actually uses this port [Unknown]
Other/unofficial uses
community gloss "Virtual Software Library Master Password protocol" from Cisco NBAR protocol-pack index and port-lookup aggregators, not confirmed against a primary IANA or vendor source [Likely, unverified] — https://www.speedguide.net/port.php?port=312, https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_nbar/prot_lib/config_library/pp620/nbar-prot-uv620.html
Security implications
no confirmed protocol, no confirmed software deployment, no confirmed malware/trojan association reported by auditmypc.com's generic dataset; essentially negligible scan activity
Typically seen on
no confirmed deployments identified; sparse legacy IANA registration [Unknown]
- Analyst note
- an open 312/udp is statistically rare and has no confirmed legitimate application; treat it as worth investigating rather than expected.
Service assignments.
| Name | Protocol | Description | Open frequency |
|---|---|---|---|
| vslmp | UDP | — | 0.06% |
| vslmp | TCP | — | 0.00% |
Service assignments from the IANA Service Name and Transport Protocol Port Number Registry, with open-frequency data from nmap-services.