498
Summary
- // if you see it open
- No CVE referencing 498/tcp is recorded in the NVD as of an August 2026 search. AuditMyPC hosts a dedicated lookup page for tcp-port-498, but its verdict/malware-tier content did not load in this search, so no malware association is claimed either way. With no documented legitimate use and near-zero scan prevalence, an open 498/tcp warrants investigation rather than assumption of routine traffic.
- // analyst note
- an open 498/tcp has no documented legitimate use and is essentially never seen in scan data — investigate rather than assume routine traffic.
About port 498/tcp.
Port 498/tcp is IANA-registered under the short service name siam, assigned to Philippe Gilbert, but IANA publishes no protocol specification, RFC reference, or expanded description for it, so what actually runs on the port is Unknown. There is no evidence tying any current software or public-facing standard to this registration, so it should not be assumed safe or appropriate to expose to the public internet.
The registry entry dual-registers 498 on both TCP and UDP under the identical name siam, with a blank Reference column and no recorded registration date. IANA's public CSV export lists only the bare service name; there is no expanded description text for siam in the current registry.
One third-party aggregator, SpeedGuide, separately lists port 498 under the label iso-ill (ISO Interlibrary Loan Application Protocol) in some of its own listings. Primary sourcing resolves this outright: IANA registers iso-ill on 499/tcp and 499/udp, not on 498 — the aggregator listing is an off-by-one against the adjacent registry row, not a genuine alternate use of this port. Port 498 is siam on both transports; SpeedGuide's own port-498 page otherwise echoes only the bare IANA siam name, consistent with sibling 498/udp's finding for the same aggregator.
Scan telemetry shows the port is essentially never observed open: nmap-services records an open-frequency of 0 for 498/tcp — a measured reading, not an absence of data — and 0.000461 for 498/udp, both far below any actively used service. No CVE referencing 498/tcp was found in the NVD as of an August 2026 search, and no vendor documentation ties a specific application to this port.
- IANA assignment
siam— no expanded description; reference (blank — no RFC cited); assignee Philippe Gilbert; dual-registered 498/tcp + 498/udp [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry siam/498/tcp, the IANA Service Name and Transport Protocol Port Number Registry siam/498/udp- Range class
- well-known (0–1023) [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=498
- Prevalence
- nmap-services open-frequency 498/tcp = 0 (measured/sampled, not observed open); 498/udp ≈ 0.000461 [Confirmed] — this site's own tooling
- Related ports
- none documented as a companion service to 498 [Unknown]
Primary use
Unknown — IANA publishes no protocol specification or expanded description beyond the bare service name siam; no documented software or standard corresponds to it
Other/unofficial uses
none — a third-party aggregator (SpeedGuide) lists port 498 under iso-ill in some of its listings, but that is an off-by-one against the adjacent registry row: iso-ill is registered on 499/tcp and 499/udp, not 498; port 498 is siam on both transports [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry iso-ill 499/tcp, the IANA Service Name and Transport Protocol Port Number Registry siam 498/tcp
Security implications
no CVE located in the NVD for 498/tcp as of an August 2026 search; AuditMyPC's dedicated lookup page for this port did not return its verdict content in this search, so no malware association is claimed
Typically seen on
no documented deployment context; near-zero scan prevalence suggests the port is essentially never open in practice [Unknown]
- Analyst note
- an open 498/tcp has no documented legitimate use and is essentially never seen in scan data — investigate rather than assume routine traffic.
About port 498/udp.
Port 498/udp carries the IANA-registered service name siam, but no protocol specification, vendor documentation, or observed real-world usage exists beyond the bare registration, so whether it belongs on the public internet or should stay internal cannot be determined from available sources.
IANA lists 498 as dual-registered on both tcp and udp under the name siam, with assignee Philippe Gilbert and a blank Reference column — there is no RFC or protocol document cited for it. Third-party port-list mirrors (SpeedGuide, my-addr.com, subnetonline.com) all just echo the same bare IANA name and registrant contact rather than adding any independent description.
A recurring web-search auto-summary claim that 498/udp is "used for remote token-ring administration" could not be traced to any actual fetched page content across IANA, SpeedGuide, subnetonline.com, or my-addr.com, and is treated here as an unverifiable search-summarizer artifact rather than a sourced finding.
nmap-services records an open-frequency of 0.000461 for 498/udp and exactly 0 for 498/tcp — a real sampled reading, not an absence of data. Some scanned hosts have been observed with 498/udp open even though no known software has been identified as the cause.
- IANA assignment
siam— description "siam"; reference (blank — no RFC cited in IANA registry); assignee Philippe Gilbert; dual-registered 498/tcp + 498/udp [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry siam 498/udp- Range class
- well-known (0–1023) [Confirmed]
- Prevalence
- nmap-services open-frequency 498/udp = 0.000461; 498/tcp = 0 (sampled, not observed open) [Confirmed] — this site's own tooling
- Related ports
- none specifically documented for this thinly-registered service [Unknown]
Primary use
Unknown — no protocol specification, RFC, or vendor documentation found beyond the bare IANA name registration
Other/unofficial uses
none found; a web-search auto-summary claim of "remote token-ring administration" could not be traced to any fetched source and is not treated as a finding [Unknown]
Security implications
no CVE recorded in NVD as of an August 2026 search; no malware/trojan family found associated with 498/udp in trojan-port reference lists as of an August 2026 search [Likely]
Typically seen on
Unknown — no documented deployment pattern found [Unknown]
- Analyst note
- 498/udp shows a nonzero but small scan-observed frequency with no known legitimate application behind it — treat an open instance as worth investigating rather than assuming benign or malicious intent.
Service assignments.
| Name | Protocol | Description | Open frequency |
|---|---|---|---|
| siam | UDP | — | 0.05% |
| siam | TCP | — | 0.00% |
Service assignments from the IANA Service Name and Transport Protocol Port Number Registry, with open-frequency data from nmap-services.