portknackningar

Portknocking is a stealthy technique used to open up network ports on a server or firewall. Instead of leaving a port open and accessible to the internet, it remains closed until a specific sequence of connection attempts is made to a predefined set of other ports. This sequence acts like a secret knock. For example, a user might attempt to connect to port 1000, then port 2000, and finally port 3000. If the server receives these connection attempts in the correct order and within a certain timeframe, it will then open a different, target port, such as SSH (port 22), allowing the user to connect. Once the connection is established, the target port may be closed again after a period of inactivity or when the user disconnects.

The primary advantage of portknocking is enhanced security. By keeping the desired service port closed by default, it becomes invisible to port scanners and potential attackers. This significantly reduces the attack surface, as unauthorized users cannot even see that the port is available, let alone attempt to exploit vulnerabilities. The sequence of connection attempts is typically not logged by standard network services, adding to its stealthy nature. However, implementing and managing portknocking can add complexity to network administration. It requires careful configuration of both the client and server to ensure the correct sequence is recognized and that legitimate users can access the services. If the knock sequence is forgotten or mistyped, access can be temporarily lost.