port:9 labs

Welcome to port:9, a dedicated space for exploring the intricacies of cybersecurity.

This blog focuses on cyber security topics, encompassing offensive security. My goal is to share in-depth knowledge and practical insights that add value to the security community.

If you have feedback, questions, or wish to connect, feel free to reach out me.

What is port 9?

The name port:9 is inspired by the historical Internet standard, RFC 863: The Discard Protocol.

Defined in 1983 by J. Postel, the Discard Protocol is a simple yet fundamental service originally used for debugging and measurement. It operates on port 9 (for both TCP and UDP) and its sole function is to receive data and silently discard it without sending a response.

Here is an excerpt from the original specification regarding the TCP service:

TCP Based Discard Service

One discard service is defined as a connection-based application on TCP. A server listens for TCP connections on TCP port 9. Once a connection is established, any data received is thrown away. No response is sent. This continues until the calling user terminates the connection.

While it is mostly a relic of early network testing, I find it to be a fitting metaphor—sometimes in cybersecurity.

✈ Read the full RFC 863 specification