Basic Linux Commands for Pentesters

Linux commands form the foundation of penetration testing, allowing security professionals to navigate systems, gather information, and execute tests effectively.

This quick guide covers essential Linux commands that every pentester should know.

System Navigation & Information Gathering

• pwd – Shows current directory location
• ls -la – Lists all files including hidden ones with permissions
• cd – Changes directories
• whoami – Displays current user
• uname -a – Shows system information

File Operations

• cat – Reads file contents
• grep – Searches text patterns in files
• touch – Creates empty files
• cp – Copies files
• mv – Moves or renames files

Network Commands

• ifconfig / ip addr – Shows network interfaces
• netstat -tuln – Lists open ports
• ping – Tests network connectivity
• traceroute – Traces packet route
• nmap – Scans network ports

Process Management

• ps aux – Lists running processes
• top – Shows real-time process activity
• kill – Terminates processes

File Permissions

• chmod – Changes file permissions
• chown – Changes file ownership
• sudo – Executes commands with elevated privileges

Text Processing

• nano / vim – Text editors
• head – Shows first lines of file
• tail – Shows last lines of file
• sort – Sorts text files

Practical Tips

• Use tab completion to speed up command typing
• Press Ctrl+R to search command history
• Create aliases for frequently used commands
• Use man pages (man command) for detailed information

Learn these commands in a test environment before using them in actual penetration tests.

Advanced Command Usage

Command Chaining

• && – Executes next command if previous succeeds
• || – Executes next command if previous fails
• ; – Executes commands sequentially
• | – Pipes output of one command to another

Data Collection

• tcpdump – Captures network traffic
• wireshark – Analyzes network packets
• strings – Extracts readable characters from files
• dd – Converts and copies files

Remote Access

• ssh – Secure shell connection
• scp – Secure file copy
• nc – Netcat for networking utility
• rsync – Remote file synchronization

Automation and Scripting

Bash Scripting Basics

• #!/bin/bash – Shebang for bash scripts
• chmod +x script.sh – Makes script executable
• ./script.sh – Executes script
• source script.sh – Runs script in current shell

Conclusion

Mastering Linux commands is crucial for effective penetration testing. Start with basic commands and gradually progress to more advanced operations. Regular practice in controlled environments helps build confidence and proficiency. Remember to always follow ethical guidelines and obtain proper authorization before conducting security tests.

Keep documentation of commonly used commands and create custom scripts to automate routine tasks. Stay updated with new tools and techniques through continuous learning and community engagement.

FAQs

1. What is the command to list files with hidden items in Linux?
   The ls -la command shows all files including hidden ones, with detailed information including permissions, owner, size, and timestamps.
2. How do you search for files containing specific text in Linux?
   Use grep -r “search_text” /path/ to recursively search for text in files, or find /path/ -type f -exec grep “search_text” {} ;
3. What command displays real-time system processes?
   The top command shows real-time system processes, while htop provides an enhanced interactive process viewer with color and additional features.
4. How do you check network connections in Linux?
   Use netstat -tuln to display active network connections, listening ports, and network statistics. Additionally, ss -tuln provides similar information with newer syntax.
5. What command captures network traffic?
   tcpdump -i interface_name captures and analyzes network traffic. For example, tcpdump -i eth0 captures traffic on the eth0 interface.
6. How do you check system users and their privileges?
   cat /etc/passwd shows all system users, while sudo -l displays current user’s sudo privileges. The id command shows user and group IDs.
7. What command shows disk usage and available space?
   df -h displays disk space usage in human-readable format, while du -sh /path/ shows directory size.
8. How do you find files with specific permissions?
   find /path/ -perm mode searches for files with specific permissions. For example, find / -perm -4000 locates SUID files.
9. What command helps monitor system logs in real-time?
   tail -f /var/log/filename continuously monitors log files in real-time. For system logs, tail -f /var/log/syslog is commonly used.
10. How do you check running services and their status?
    systemctl list-units –type=service shows all services, while service servicename status displays specific service status.

Author: Editor