Security tool


On a recent podcast episode, we ran an informal survey of what most listeners thought was their most essential open source tool. The overwhelming winner was the humble secure shell, SSH, the remote command-line client and server that many have been using for decades. SSH is super secure and easy to use, often configured by a distribution at install time, which enables even beginners to start using their machines remotely. But SSH can also be a victim of its own success. Its ubiquity makes it a common attack vector, as anyone who runs an SSH server and happens to look at the logs will attest. Your logs will be full of automated attempts to guess your username and password combinations, a situation not helped when even distributions such as older versions of Raspberry Pi OS used the same default password and username combinations.

All of this can be mitigated with a properly configured SSH server, swapping passwords for encryption keys, for instance, and changing the default ports. But unless you're an expert, it can be difficult to know whether you've exchanged one set of problems with another, which is where the aptly named ssh-audit can help. It's a command that can deeply check your SSH configuration by analyzing the connection rather than parsing the configuration file. This allows you to detect what is actually happening, as well as passively monitor for client and server-side vulnerabilities on incoming and outgoing connections, even when you don't control the server. The output is verbose and will detail which algorithms are being used, which should be disabled, and which removed, alongside which keys are detected. It's a glut of information but an incredibly valuable insight into the state of the connections on which we all rely.

Project Website

While ssh-audit goes into a lot of detail, you can find an excellent hardening guide on their website if you need advice on how to improve your SSH configuration.

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