Port 79 (Finger)

Port 79 (TCP) is associated with the Finger protocol, a simple network protocol designed to provide information about users logged into a system or information about a specific user. Originally developed in the early days of ARPANET, Finger allows users to query a server and retrieve information such as the user's full name, login time, idle time, terminal line, and office location/phone number. The protocol operates by sending a simple text-based request to the Finger server on port 79. The server then processes the request and returns a text-based response containing the requested user information or a general status message. A request can be as simple as a username, or it can include options to request more detailed information.

The Finger protocol is relatively straightforward. A client connects to the server on port 79, sends a query (typically a username or an empty string for a list of users), and receives a response. The response format is loosely defined, often including fields such as login name, real name, terminal, idle time, login time, and office location. The protocol lacks any built-in authentication or encryption mechanisms, making it vulnerable to various security risks. The basic operation involves a simple TCP connection, a text-based request, and a text-based response, making it easy to implement but also easy to exploit if not properly secured.

## Firewall Recommendations

Due to the inherent security risks and limited modern use of the Finger protocol, it is generally recommended to block port 79 (TCP) at the firewall. If the Finger service is absolutely necessary for legacy applications, it should be isolated within a secure internal network, and access should be strictly controlled. Consider using a modern, more secure alternative for user information retrieval. If you must allow the service, ensure the server software is up-to-date with the latest security patches, implement strict input validation on user queries, and consider using a wrapper or proxy to filter potentially malicious requests. Monitor network traffic for suspicious activity on port 79.