674
Summary
- // if you see it open
- Never widely adopted (webmail and other config mechanisms displaced it). An open 674 is legacy.
- // analyst note
- An open 674 almost certainly indicates an old ACAP server or a port-scan false positive; investigate as legacy.
About port 674.
Port 674/tcp is registered with IANA as acap with the description "ACAP" and a blank reference field, dual-registered on TCP and UDP; this was verified live against the IANA Service Name and Transport Protocol Port Number Registry (assignee Chris Newman, modified 2010-10-15, reference column blank). ACAP, the Application Configuration Access Protocol, is defined in RFC 2244 (November 1997, Standards Track), whose section 2.1 states that when TCP is used an ACAP server listens on port 674, and ACAP URLs default to port 674; related work includes RFC 6075 (the IANA ACAP Vendor Subtrees Registry) and the acap: URI scheme. Its purpose is to let a client — for example an email client — remotely store and retrieve program option, configuration, and preference data such as bookmarks, address books, and IMAP client settings from a central server, so that a user gets the same configuration on any machine; features include inheritance of default values and access control lists. RFC 2244 is ACAP's defining specification, not the IANA registry reference — the registry reference column for 674 is blank. Security-wise ACAP never achieved wide adoption — the rise of webmail and other configuration mechanisms displaced it — so an open 674 is rare and legacy. For an analyst, an open 674 almost certainly indicates an old ACAP server or a port-scan false positive and should be investigated as legacy.
- IANA assignment
acap— "ACAP"; registry reference field blank (RFC 2244 is the ACAP defining spec, not the IANA reference); dual-registered 674/tcp + 674/udp [IANA-assigned; verified live against the IANA CSV] — IANA Service Name and Transport Protocol Port Number Registry- Range class
- well-known (0–1023)
- Prevalence
- rare/legacy; nmap-services de-facto low [Well-established] — nmap-services file
- Related ports
- 143 (IMAP — ACAP was conceived to complement IMAP email clients)
Primary use
remote storage/retrieval of client configuration and preferences (RFC 2244)
Other/unofficial uses
none meaningful [Well-established]
Security implications
never widely adopted; an open 674 is legacy [Well-established]
Typically seen on
legacy ACAP servers
- Analyst note
- An open 674 almost certainly indicates an old ACAP server or a port-scan false positive; investigate as legacy.
Service assignments.
| Name | Protocol | Description | Open frequency |
|---|---|---|---|
| acap | UDP | — | 0.07% |
| acap | TCP | ACAP server of Communigate (www.stalker.com) | 0.01% |
Service assignments from the IANA Service Name and Transport Protocol Port Number Registry, with open-frequency data from nmap-services.