Nessus is a pretty strong remote security scanning tool which scans devices and raises an alert if it discovers any vulnerabilities that hackers could use to gain access to a computer you have connected to a network. Within days of the vulnerabilities being released to the public, there will be plugins for new vulnerabilities. Nessus utilizes Nmap for port scanning.
Let's take a step-by-step look at how to scan a specified network and hosts.