Port Scanning

This is the art of finding out the entire list of open ports on the target system.

A computer has mainly 2 types of ports
1) Hardware ports
2) Virtual Ports
Hardware ports :
These are the physical doors through which the devices are connected.

Virtual Ports :
These are the virtual doors behind which different softwares are running.Every application opens a port to run.The security of that application determines the vulnerability of that port.

port scanning can be done to gather information regarding the
List of open ports
Names and Versions of services
OS information

So how can we port scan a target.?
Method 1:
Manually connect to the target using telnet and find the open ports.This method is very tedious.We need to connect to each and every port manually to find out the open ports.This may take much time.

Method 2:
To avoid the unnecessary time lag due to the first method we can use automated tools to port scan a target system.some good tools are posted in the end of this post.Do check it.

 The information gathering using the port scanning is mainly done using the daemon banner grabbing.Daemon banner grabbing is nothing but study of the banner shown by the application when we try to connect to an open port.

If we get a banner then the port is open.If we get some error messages the port is most likely to be closed.

Nmap
strobe
Netcat
superscan
ipeye
TCP_scan
UDP_scan