Port scanning

After live systems have been identified, it's time to check for any open ports on the target.

So, what is a port? First, let's assume that every host on our network has a unique address assigned to it, known as an IP address. This address is a unique number assigned to a host to differentiate it from other hosts on the network.

Of course, we also need to concern ourselves with when information is sent from system to system and how a computer knows how to accept that information. The answer is ports. I will use the 192.168.1.4 IP address as our target system:

192.168.1.4:80

So, how many ports are available on a system? There are 65,535 port numbers. Some network services uses TCP ports to ensure their data is delivered to the recipient, while other network services use UDP for fast communication but do not guarantee a fast delivery like TCP. The port ranges which we use are as follows:

• Well-known ports range from 1 - 1024. These ports are most commonly used, an example would be port...