Challenge list

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…

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.…

Network SecurityLevel 1★☆☆☆☆

08. Network Basics - Learn Port Numbers

Networks use port numbers to identify services. For example, a web server (HTTP) usually uses port 80, and encrypted…

10 ptsOpen challenge

ProgrammingLevel 1★☆☆☆☆

09. Python Automation - File Reading

In security work, programming is essential for processing large amounts of data. In this challenge, you'll use Python…

CryptographyLevel 1★☆☆☆☆

11. Decode the Caesar Cipher

The Caesar cipher is one of the oldest classical ciphers used by Julius Caesar. It encrypts by shifting alphabet…

CryptographyLevel 1★☆☆☆☆

14. ROT13 Magic

ROT13 (Rotate 13) is a type of Caesar cipher that shifts the alphabet by 13 letters. Interesting feature of ROT13:…

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-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-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-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-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-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-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-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-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-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-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-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…