Daily Blog #779: Sunday Funday 3/16/25

As I sit here reflecting on my recent adventures, one thing becomes glaringly apparent: it's been far too long since I've taken on a Linux challenge. Determined to shake things up, this week we're going to explore the world of SSH tunnels and all the interesting artifacts that come with them.

For those who may be new to the world of Linux security, let's start from the basics. When someone authenticates via SSH into a Linux system, they leave behind a treasure trove of digital breadcrumbs. These breadcrumbs, or artifacts, can provide valuable insight into an attacker's activities and can even be used to track their movements across different systems.

Let's take a closer look at some of the key artifacts left behind on both server and client-side when someone uses SSH to authenticate.

Server-Side Artifacts

1. SSH Key Exchange Logs:

When an attacker authenticates via SSH, their public key is exchanged with the server's private key. These logs can provide valuable information about the attacker's identity and even reveal any customizations they may have made to their public key.

Client-Side Artifacts

1. Bash History Logs:

When an attacker connects via SSH, their terminal history is often preserved on the client-side. These logs can provide a wealth of information about the attacker's actions, including any commands they may have executed or files they may have accessed.

SSH Tunnel Artifacts

1. SSH Tunnel Logs:

When an attacker creates an SSH tunnel between two systems, they often leave behind logs that detail the connection's establishment and any data exchanged during the session. These logs can be used to track the flow of data between the two systems.

Tunnel Creation Artifacts

1. SSH Tunnel Files:

Depending on the specific configuration, SSH tunnels may create additional files or sockets that are left behind on the client and server sides. These files can provide valuable information about the tunnel's creation and any data it may have transferred.

Tracking the Attackers

By examining these artifacts in detail, security professionals can piece together a timeline of an attacker's activities and even track their movements across different systems. This can be particularly useful in investigating and preventing future attacks.

This week, we challenge you to take on your own Linux challenge. Document all the logs and artifacts left behind by SSH-ing into a Linux system and creating a tunnel between two systems. What secrets will you uncover? Share your findings with us in the comments below!