What you will learn
- Investigate systems with core commands
- Understand files and permissions
- Find evidence in logs and running processes
Hands-on Linux Security CTF Challenges
Practice Linux commands, permissions, processes, logs, and privilege boundaries through focused security challenges.
Linux challenges
39 challenges available.
Linux Level 1 03. Linux First Steps - Find the File
You've connected to a Linux server! There's a file with the flag in the home directory. Use basic commands to find the…
Linux Level 1 04. Find the Hidden File
In Linux, files whose names start with "." (dot) are "hidden files" and are not displayed with the regular ls command.…
Linux Level 1 Linux-01. Grep the Needle Out of the Log Pile
Under /var/log/app there are many date-stamped log files, and the flag is hidden in a single ERROR line among them.…
Linux Level 1 Linux-SSH Key Hunt. Discovering a Hidden Private Key File
A file resembling a private key is hidden deep inside an application's configuration directory. Use find to track it…
Linux Level 1 Linux-Archive. Extracting a Secret from a Tarball
A compressed archive (.tar.gz) in the home directory contains a file with the flag hidden inside. Extract it with tar…
Linux Level 1 Linux-Custom. Inspecting a Scheduled Backup Script
Inspect the scheduled script placed under /usr/local/bin along with the cron entry that registers it. Comments inside…
Linux Level 1 Linux-Service Config. Digging into Nginx Configuration Files
Several service configuration files exist under /etc. Some are decoys while others hold real clues, so read through…
Linux Level 1 Linux-Symlink Basics. Following a Chain of Links to the End
A single chain of symbolic links connects several files. Follow the chain with ls or readlink until you reach the real…
Linux Level 1 Linux-Disk Usage. Tracking Down a Bloated File
A hidden directory contains an unusually large file. Use du or find's size options to track it down and inspect its…
Linux Level 1 Linux-Permissions Basics. Running a Script with No Execute Bit
A script file lacks execute permission. Check its permissions, add execute permission with chmod, and then run it.
Linux Level 1 Linux-File Type Disguise. Unmasking Files with the file Command
A file with a .jpg extension may actually contain plain text. Use the file command to spot files whose extension does…
Linux Level 1 Linux-Process Basics. Checking a sleep Command's Arguments
Find the process with the target command-line argument among several processes running in the background. This…
Linux Level 1 Linux-Deep Search. Discovering a Deeply Nested File
A single file containing the flag is hidden deep inside many nested directories. Use the find command to locate the…
Linux Level 1 Linux-Environment Variable Basics. Checking Shell Startup Variables
One of the environment variables set when the shell starts holds the flag. Check it with the env command or echo…
Linux Level 1 Linux Basics - Permissions and SUID
Learn basic Linux commands and file permissions. Use hints to find SUID and retrieve the flag.
Linux Level 2 Linux-02. Privilege Escalation via a Sudo-Allowed Vim
Check which commands a regular user can run via sudo without a password. A well-known GTFOBins technique can let you…
Linux Level 2 Linux-03. Reading Cron Configuration Files
This system has several cron configurations (/etc/cron.d, /etc/crontab, user crontabs, and more). Inspect each…
Linux Level 2 Linux-Cron Privesc. Hijacking a Writable Root Script
Check the permissions of a cron script that root executes periodically. If a regular user can write to it, think about…
Linux Level 2 Linux-Systemd. Checking a Service Unit's Environment Variable
A systemd unit file can set environment variables in its [Service] section. Inspect the registered service definition…
Linux Level 2 Linux-Symlink Maze. Navigating a Branching Path
Several directories are connected in a tangled web of symbolic links. Without being misled by decoy hint files, follow…
Linux Level 2 Linux-Script Debug. Fixing a Broken Bash Script
This script has several intentional bugs (typos, syntax mistakes) and fails to run to completion. Use bash's debugging…
Linux Level 2 Linux-Network Basics. Connecting to a Listening Port
A background service on this system is listening on a specific port. Identify the port with ss/netstat and connect to…
Linux Level 2 Linux-Backup Finder. Spotting the Real Temp File
The project directory contains several decoy backup/temp files ending in .bak, .tmp, or ~. The real flag is hidden…
Linux Level 2 Linux-Pipeline. Narrowing Down Logs with grep and awk
The access log contains many lines, several of which include the flag. Chain commands together with pipes (|) to…