Port 148 is assigned to CRONUS-SUPPORT, the support service for a distributed operating system called CRONUS. If you have never heard of CRONUS, you are in good company. Almost no one has. But port 148 has been holding this reservation in the IANA registry since at least 19921, and the system it was built for tells us something about what the early Internet thought it was going to become.
What Runs on Port 148
Nothing, almost certainly. Not on your machine, not on any machine you are likely to encounter. Port 148 is registered for both TCP and UDP under the service name "cronus" with the description "CRONUS-SUPPORT."2 It was intended to carry support traffic for the CRONUS distributed operating system, a research project that ended decades ago.
If something is listening on port 148 on your network today, it is not CRONUS. It is either a misconfiguration, a proprietary application reusing the port, or something you should investigate immediately.
The CRONUS Distributed Operating System
CRONUS was designed and built by BBN Laboratories, beginning in 1981, under contract for the Air Force Rome Air Development Center (RADC)3. BBN (Bolt Beranek and Newman) was the same organization that built the Interface Message Processors for the original ARPANET. When they reserved a port number, it meant something.
The project's ambition was large: create a coherent distributed operating system that could span clusters of heterogeneous computers interconnected by local area networks. Different machines, different architectures, different operating systems, all presenting a unified interface for resource sharing and distributed application development.
The Object Model
The cornerstone of CRONUS was its object model3. Every shared resource, whether a file, a process, a device, or a service, was represented as an abstract, typed object managed by a "manager" process somewhere on the network. When a program needed to interact with a resource, it invoked operations on that object. The system handled location transparency: the invoker did not need to know which machine held the resource.
This was 1981. Object-oriented programming was still finding its vocabulary. The idea of treating distributed resources as objects with typed operations and transparent location was genuinely ahead of its time.
Key People
The principal researchers included Richard E. Schantz and Robert H. Thomas of BBN Laboratories. Bob Thomas authored the interhost protocol specification for CRONUS/DIAMOND interprocess communication in September 19831, which is the document referenced in the IANA port assignment. Thomas had been working on distributed computing at BBN since at least 1972, when he began a project to bring distributed computing to the TENEX operating system4.
The Port Assignment
In RFC 1340 (July 1992), authored by J. Reynolds and J. Postel, port 148 appears as1:
Reference [135] points to Thomas's 1983 interhost protocol document. The contact identifier JXB was associated with Apollo Computers. The assignment was carried forward through a long chain of "Assigned Numbers" RFCs stretching back through the 1980s.
The Name "Jargon"
Some port databases list the description for port 148 as "Jargon" rather than "CRONUS-SUPPORT." This appears to be a labeling inconsistency across different reference sources. The IANA registry and the RFC lineage consistently identify it as CRONUS-SUPPORT with the service keyword "cronus."
Why Port 148 Still Matters
Port 148 is a well-known port, meaning it falls in the system port range (0-1023). These ports are assigned through IETF Review or IESG Approval, the most rigorous assignment process IANA offers5. Getting a well-known port number was not trivial even in the 1980s.
The fact that port 148 remains assigned to a system that no longer exists tells you something about how the Internet's numbering system works. Port assignments are rarely reclaimed. The registry is a geological record: each layer preserves the ambitions and infrastructure of its era. Port 148 is from the stratum where researchers at BBN thought heterogeneous distributed computing would be the next frontier. They were right about the idea. CRONUS just was not the version that survived.
Checking Port 148
To see if anything is listening on port 148 on your system:
Linux/macOS:
Windows:
If a service is listening on port 148 and you did not put it there, investigate. This port has no modern legitimate use that would explain unexpected traffic.
Security Considerations
Some threat intelligence databases have flagged port 148 as historically associated with malware communication6. This is not unusual for obscure well-known ports. Attackers sometimes choose little-known assigned ports precisely because they are unlikely to be monitored. If you see traffic on port 148, do not assume it is benign just because the port has an official IANA assignment.
Related Ports
Port 148's neighbors in the IANA registry reflect the same era of early Internet infrastructure research:
- Port 146 (ISO-TP0): ISO Transport Protocol Class 0
- Port 147 (ISO-IP): ISO Internet Protocol
- Port 149 (AED-512): AED 512 Emulation Service
- Port 150 (SQL-NET): SQL-NET, an early database networking protocol
These are all artifacts of a period when the port registry was being populated with research projects and emerging standards, many of which did not survive into the modern Internet.
Frequently Asked Questions
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