Checking for live systems and their ports

Scanning for live systems can be very loud or noisy on the network, but if you can do it strategically, the target might never see we're going through their network looking for targets.

Now, let's look at different ways to check for live systems.

ICMP sweep/ping sweep

This is the most common way to check for live systems. Like a sonar ping in a submarine, we ping and hope we get a return, which tells us how far away the target is or where the target is located. A standard ping uses the ICMP protocol, which is not only well known but also very noisy on the network – so much so that most IT professionals will block ICMP traffic as a deterrent.

Port scanning

Just because a machine does not respond to a ping sweep or an ICMP sweep doesn't mean it's not there. So, we can perform port scans in various ways and specify IP addresses. We can still try to check if it responds. We'll show you how to do...