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.
LinuxLevel 103. 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…
LinuxLevel 104. Find the Hidden File
In Linux, files whose names start with "." (dot) are "hidden files" and are not displayed with the regular ls command.…
LinuxLevel 1Linux-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.…
LinuxLevel 1Linux-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…
LinuxLevel 1Linux-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…
LinuxLevel 1Linux-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…
LinuxLevel 1Linux-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…
LinuxLevel 1Linux-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…
LinuxLevel 1Linux-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…
LinuxLevel 1Linux-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.
LinuxLevel 1Linux-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…
LinuxLevel 1Linux-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…
LinuxLevel 1Linux-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…
LinuxLevel 1Linux-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…
LinuxLevel 1Linux Basics - Permissions and SUID
Learn basic Linux commands and file permissions. Use hints to find SUID and retrieve the flag.
LinuxLevel 2Linux-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…
LinuxLevel 2Linux-03. Reading Cron Configuration Files
This system has several cron configurations (/etc/cron.d, /etc/crontab, user crontabs, and more). Inspect each…
LinuxLevel 2Linux-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…
LinuxLevel 2Linux-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…
LinuxLevel 2Linux-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…
LinuxLevel 2Linux-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…
LinuxLevel 2Linux-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…
LinuxLevel 2Linux-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…
LinuxLevel 2Linux-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…