What is Nessus?

Nessus is a wireless security scanning program that inspects a machine and creates a report. It finds any flaws that malevolent hackers could exploit to obtain access to any computer linked to a network.

This tool is free for non-commercial use. However, there are different solutions for enterprise use that are charged differently.

Nessus Clients provide a customizable method of scanning hosts in your environment without requiring hosts to supply credentials. The agents allow scans to be performed even when the hosts are unavailable. These agents have numerous applications.

Consider environments where standard malware security, such as antivirus software, is lacking. Nessus will help you out with scanning. The most widely used vulnerability assessment solution on the market is Nessus Professional.

This solution enables you to perform high-speed asset discovery, target profiling, configuration auditing, virus detection, sensitive data discovery, and other tasks. Nessus can be used effectively by your organization’s security departments because it runs on client devices such as laptops.

Why Nessus?

If you’re familiar with various network vulnerability scanning methods, you might be asking what makes Nessus stand out.

Nessus is free and open-source, which means you can inspect and edit the code as you see fit. Nessus, unlike other scanners, does not assume things about your web server, which might cause other scanners to overlook serious vulnerabilities.

Nessus is fairly extendable, featuring a scripting language that allows you to develop tests relevant to your system as you become more acquainted with the tool. These plugs are usually designed to identify a specific infection or vulnerability.

The Nessus team refreshes the list of vulnerabilities to search for regularly to reduce the time between an exploit getting discovered in the wild and you being able to identify it using Nessus.

When Nessus identifies a vulnerability, it will usually propose the best strategy to mitigate it.

What is a Nessus Agent?

Nessus Agents provide a customizable method of scanning hosts in your environment without requiring hosts to supply credentials. The agents allow scans to be performed even if the hosts are unavailable.

The support offered by Nessus Agents is a subset of that provided by a regular network scan.

  • Scanning of endpoints that are not always connected to the local network.
  • Analyzing assets for which you do not even have or cannot simply obtain credentials.
  • They are improving scan performance in general.

Nessus Agents support various operating systems like CentOS, Debian Linux, Ubuntu Linux, Windows Server 2008 and 2012, and Windows 7 and 8, Red Hat Enterprise Linux.

Versions And License

Nessus Professional: This version is designed for consultants, penetration testers, and security professionals. It has the capacity to scan an unlimited number of IP addresses, the freedom to use it anywhere, and sophisticated capabilities such as configuration assessment, Live Results, and custom reports.

Nessus Essentials: This version is free for scanning any environment. However, it is restricted to 16 IP addresses for each scanner.

Some other advantages of the professional version are

  • Superior Detection Increased Security.
  • Plugins offer immediate protection.
  • Scale and grow in a safe manner.
  • Budget-effective for businesses of all sizes.
  • Detailed insight into your networks.

User Interface

Nessus is composed of two components: a server named Nessus and a client that can be one of the various possibilities. The server is the side of Nessus that runs the tests, whereas the client tells the server which examines to run on which computers.

The user interface has two parts: the scan and the settings pages.

The scan page will enable us to create and manage fresh scans. There are different other tabs on the bottom left of your screen that allow you to specify a policy that applies to your scans, define plugin rules, and manage your scanners and agents.

The settings page will include configuration information to allow you to create settings for your LDAP, Proxy, and SMTP servers for additional functionality and network interaction.

Scanning vulnerabilities

Nessus performs scans by using plugins that run against each host on the network to find vulnerabilities. Plugins are distinct pieces of code that Nessus utilizes to perform specific kinds of scanning on targets. Determine which software components, such as FTP, SSH, and SMB, are vulnerable to attacks.

  • Nessus will first get the scan settings and identify the ports to be scanned, plugins to be activated, and policy preferences.
  • Nessus will then undertake host discovery to ascertain which hosts are operational. ICMP, TCP, UDP, and ARP will be the protocols utilized in host finding. You can customize these to your liking.
  • It runs a port scan on any host discovered to be online. You can also choose which ports to inspect.
  • Then, Nessus will perform service detection to identify which services are running behind these ports on each discovered host.
  • Nessus scans each host against a list of known vulnerabilities to determine which hosts have flaws.


Today’s most widely used vulnerability scanner in the cybersecurity sector is the Nessus Vulnerability Scanner. The functionality you get, particularly with the conventional version, is a complete assurance of value for money. While it is also vital to check your vulnerability hits by running different vulnerability scanners against your targets to avoid the potential for false positives, the functions of Nessus justify its popularity.