This document is a WORK IN PROGRESS.
This is just a quick personal cheat sheet: treat its contents with caution!

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Netcat

Netcat (or nc) is a command line utility that reads and writes data across network connections, using the TCP or UDP protocols. It is one of the most powerful tools in the network and system administrators arsenal, and it as considered as a Swiss army knife of networking tools.

Reference(s)

• https://wiki.archlinux.org/title/Network_tools
• https://www.linuxfordevices.com/tutorials/netcat-command-in-linux
• https://linuxize.com/post/netcat-nc-command-with-examples/
• $ man nc

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Table of contents

• Install
• Use

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Install

emergepacmanaptyumdnf

# emerge -a netcat

# pacman -S netcat

# apt install netcat

# yum install nc

# dnf install nc

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Use

• Connect via TCP (by default) to a given port (e.g. 22) on given target host (e.g. 192.168.123.123):

  $ nc 192.168.123.123 22
  

• Connect via UDP to a given port (e.g. 22) on given target host (e.g. 192.168.123.123):

  $ nc -u 192.168.123.123 22
  

• Connect to multiple ports (e.g. 22, 23, 24) on given target host (e.g. 192.168.123.123):

  $ nc 192.168.123.123 22 23 24
  

• Connect to a range of ports (e.g. 22-32) on given target host (e.g. 192.168.123.123):

  $ nc 192.168.123.123 22-32
  

• Connect, with a timeout (e.g. 2 secs), to a given port (e.g. 22) on given target host (e.g. 192.168.123.123):

  $ nc -w 2 192.168.123.123 22
  

• Connect, in scan mode (i.e. scan for listening daemons without actually sending any data to them), to a given port (e.g. 22) on given target host (e.g. 192.168.123.123):

  $ nc -z 192.168.123.123 22
  

• Connect to a given port (e.g. 22) on a given target host (e.g. 192.168.123.123), and output the hex dump of the traffic to a file:

  $ nc -o /path/to/output/file 192.168.123.123 22
  

• Send data to a given port (e.g. 8080) on a given target host (e.g. 192.168.123.123):

  $ nc 192.168.123.123 8080 < /path/to/data.txt
  

• Listen to a local port (e.g. 8080) and copy the incoming traffic to a file:

  $ nc -l 8080 > /path/to/file.txt
  

• Attach a local port (e.g. 4242) to a local shell (e.g. /bin/bash), thanks to the -e option which allow to execute a specified program when a client connects to the port. ⚠️ == But be careful with this, anybody could connect to your 4242 port and gain access to your /bin/bash shell! Consider this like a system backdoor!==⚠️:

  $ nc -l 4242 -e /bin/bash
  

  Just run $ nc 192.168.123.123 4242 to access the remote /bin/bash (e.g. on a remote target with 192.168.123.123 IP)

WIP

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