446

Port 446/tcp is IANA-registered as ddm-rdb, IBM's DDM (Distributed Data Management) service for DRDA (Distributed Relational Database Architecture) remote database access, used mainly by IBM i (AS/400, iSeries) systems and DB2 for z/OS. Because this traffic carries plaintext database credentials and queries, 446/tcp belongs on an internal or VPN-protected network, never exposed directly to the public internet.

IANA's registry dual-registers port 446 as ddm-rdb on both TCP and UDP, with the assignee and reference fields both blank — a legacy assignment that predates IANA's current documentation norms rather than one backed by a specific RFC. The registry's own description reads simply "DDM-Remote Relational Database Access."

DDM and DRDA let a client reach IBM i or DB2 for z/OS databases over the network, with port 446 serving as the base plaintext DRDA channel. IANA separately registers two companion ports: 447 as ddm-dfm ("DDM-Distributed File Management") and 448 as ddm-ssl ("DDM-Remote DB Access Using Secure Sockets"), the SSL/TLS-encrypted counterpart to 446.

IBM's own support documentation for its DB2 Table Editor, and Syniti's (formerly HiT Software) DB2-connectivity middleware, both specify opening port 446 for DRDA access — corroborating this as the port's operative modern use rather than a legacy artifact. nmap-services records an open-frequency of about 0.0075% for 446/tcp and 0.046% for 446/udp, a low but non-zero reading consistent with a niche enterprise-database port.

IANA assignment

ddm-rdb — "DDM-Remote Relational Database Access"; reference (blank — no RFC cited in IANA registry); assignee (blank — none listed); dual-registered 446/tcp + 446/udp [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry ddm-rdb 446/tcp, ddm-rdb 446/udp

Range class

well-known (0–1023); source artifact labels this the "system" range [Confirmed] — this site's own tooling (port 446 entry)

Prevalence

nmap-services open-frequency 446/tcp ≈ 0.000075 (~0.0075%); 446/udp ≈ 0.000461 (~0.046%) [Confirmed] — this site's own tooling (port 446 entry)

Related ports

447/tcp+udp ddm-dfm (DDM-Distributed File Management); 448/tcp+udp ddm-ssl (DDM-Remote DB Access Using Secure Sockets, the SSL/TLS-encrypted equivalent of 446) [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry ddm-dfm 447/tcp, ddm-ssl 448/tcp

Primary use

IBM DDM (Distributed Data Management) / DRDA (Distributed Relational Database Architecture) remote relational database access; the DRDA port for IBM i (AS/400, iSeries) and DB2 for z/OS [Likely] — https://www.ibm.com/support/pages/configuring-drda-port-run-db2-table-editor, https://support.syniti.com/hc/en-us/articles/5726217312535-1561-Securing-Ports-via-a-Firewall-in-Client-Server-TCP-Communication-with-IBM-i

Other/unofficial uses

none documented beyond the registered DDM/DRDA role

Security implications

DDM/DRDA on 446 (and companion port 447, ddm-dfm) is plaintext; IANA separately registers 448 (ddm-ssl) as the dedicated SSL/TLS-encrypted equivalent; no CVE/NVD record ties to port 446 as of an August 2026 search; an auditmypc.com IDS-signature reference is unconfirmed and not treated as a malware association [Confirmed/Likely/Unknown] — the IANA Service Name and Transport Protocol Port Number Registry ddm-ssl 448/tcp, https://www.auditmypc.com/tcp-port-446.asp

Typically seen on

IBM i (AS/400, iSeries) and DB2 for z/OS database servers; DB2 Table Editor and Syniti/HiT Software DB2-connectivity middleware clients [Likely] — https://www.ibm.com/support/pages/configuring-drda-port-run-db2-table-editor, https://support.syniti.com/hc/en-us/articles/5726217312535-1561-Securing-Ports-via-a-Firewall-in-Client-Server-TCP-Communication-with-IBM-i

Analyst note

An open 446/tcp is most plausibly IBM DDM/DRDA database access from an IBM i or DB2-for-z/OS client; because the protocol is plaintext, treat an internet-facing listener as a credential- and data-exposure risk and confirm it sits behind a firewall or VPN.

Port 446/udp is IANA-registered as ddm-rdb, described as "DDM-Remote Relational Database Access." As a relational-database access protocol, it belongs on internal or trusted networks rather than being exposed directly to the public internet.

IANA registers ddm-rdb identically on 446/tcp and 446/udp: same service name, same description, and both rows carry a blank Assignee and a blank Reference field. No RFC or other specification document is cited, and no registration or modification date is recorded for either transport.

Port 446 sits inside a small cluster of related "ddm"-prefixed registrations: 447/tcp+udp (ddm-dfm, "DDM-Distributed File Management") and 448/tcp+udp (ddm-ssl, "DDM-Remote DB Access Using Secure Sockets") are both assigned to Steven Ritland, and neighboring 449/tcp+udp (as-servermap) is assigned to Barbara Foss — none of the four carry an RFC reference either.

this site's own tooling, built from nmap-services, records an open-frequency of roughly 0.0075% for 446/tcp and roughly 0.046% for 446/udp — both rare, with the UDP reading about six times the TCP one. The registry gives no indication which transport, if either, sees legitimate use today.

SANS Internet Storm Center tracks port 446 across both transports as ddm-rdb, and as of an August 2026 search classifies it as ordinary background scanning with a non-elevated status — no CVE and no documented malware association. Secondary port-lookup aggregators offer contradictory, unsourced guesses about what generates this traffic; neither is corroborated, so no specific current software is credited.

IANA assignment

ddm-rdb — "DDM-Remote Relational Database Access"; reference (blank — no RFC cited in IANA registry); assignee blank; dual-registered 446/tcp + 446/udp with identical service name and description

[Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry ddm-rdb 446/tcp, ddm-rdb 446/udp

Range class

well-known (0–1023); source artifact labels this the "system" range [Confirmed] — this site's own tooling (port 446 entry)

Prevalence

this site's own tooling (nmap-services derived) open-frequency 446/tcp ≈ 0.000075 (~0.0075%), 446/udp ≈ 0.000461 (~0.046%) — both rare, UDP roughly 6x the TCP reading [Confirmed] — this site's own tooling (port 446 entry)

Related ports

446/tcp (identical dual registration, same name and description); 447/tcp+udp ddm-dfm and 448/tcp+udp ddm-ssl (same "ddm" registration block, both assigned to Steven Ritland); 449/tcp+udp as-servermap (adjacent, assigned to Barbara Foss)

[Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry ddm-dfm 447/tcp, ddm-ssl 448/tcp, as-servermap 449/tcp

Primary use

registered for DDM-Remote Relational Database Access; the registry supplies only the name and description, with no protocol specification, RFC, or registration date [Confirmed(registration text)/Unknown(protocol detail)] — the IANA Service Name and Transport Protocol Port Number Registry ddm-rdb 446/udp

Other/unofficial uses

none corroborated — as of an August 2026 search, no credible primary or community source ties specific current software to this port; contradictory unsourced aggregator guesses (Microsoft DTC vs. Dell Data Protection Manager) were discarded rather than reported as fact [Unknown]

Security implications

no CVE/NVD record as of an August 2026 search; SANS ISC tracks port 446 (both transports) as ddm-rdb with an ordinary, non-elevated (green) scanning posture; auditmypc.com's port-446 page records Virus/Trojan: No (cited for the negative finding only)

Typically seen on

no confirmed current deployments; a response is more consistent with routine background-scan noise than a confirmed live ddm-rdb service [Unknown]

Analyst note

Treat a response on 446/udp as most likely routine background scanning rather than a confirmed live service — no current software is reliably attributed to this port; if genuine relational-database access traffic is ever confirmed here, it still has no legitimate reason to face the public internet.