Port 618 is officially assigned to DEI-ICDA (Data Exchange Interface - ICDA) on both TCP and UDP by IANA. But that's about all anyone knows.
The Mystery
Search for DEI-ICDA anywhere on the Internet and you'll find the same thing: port listings that repeat "DEI-ICDA" without explaining what it is. No documentation. No RFC. No company claiming to have built it. No users asking questions about it.
This port was registered at some point in the past, given an official assignment, and then... nothing. The service either never saw widespread use, was abandoned, or operated so quietly that it left no digital footprint.
What We Know
Port 618 sits in the well-known ports range (0-1023), which means it was registered with IANA for a specific service. This range is supposed to be reserved for standardized, important protocols—the infrastructure services that networks depend on.
But DEI-ICDA isn't one of them. At least not anymore. Or maybe it never was.
Official assignment:
- Port: 618
- Service name: dei-icda
- Protocol: TCP and UDP
- Description: DEI-ICDA (Data Exchange Interface)
- Status: Registered, but essentially unknown
Security Note
Some security databases have flagged port 618 due to historical malware activity. This doesn't mean the port itself is dangerous—malware can use any port. But if you see unexpected traffic on port 618, it's worth investigating since legitimate DEI-ICDA traffic is essentially nonexistent.1
Why Forgotten Ports Matter
Port 618 is a reminder that the Internet's infrastructure isn't just about what's actively being used. It's also about what was tried and abandoned. What was registered with optimism and then forgotten.
The IANA registry contains thousands of ports. Some carry email, web traffic, secure connections—the protocols that define the modern Internet. Others, like port 618, are archaeological artifacts. They were assigned, they exist in the official record, but they don't carry anything anymore.
How to Check What's Using Port 618
On most systems, you can check if anything is listening on port 618:
Linux/Mac:
Windows:
If you find something listening on port 618 and you didn't configure it, investigate. Legitimate DEI-ICDA services are so rare that any traffic on this port is worth questioning.
The Well-Known Range
Port 618 belongs to the well-known ports (0-1023). This range is controlled by IANA and requires formal registration. Getting a well-known port assignment is supposed to mean something—that your protocol is important enough, standardized enough, used enough to deserve a reserved spot.
DEI-ICDA got that spot. And then vanished.
Related Ports
Near port 618, you'll find:
- Port 617: SCO Desktop Administration Server
- Port 619: Compaq EVM (another mostly forgotten service)
- Port 620: SCO WebServer Manager
The 600s are full of ports like this—services that were important in the 1990s and early 2000s, tied to companies and protocols that have since faded.
Frequently Asked Questions
- IANA Service Name and Transport Protocol Port Number Registry
- Port 618 Security Information1
- Port 618 Overview
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