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.

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The Significance of 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