Nessus is one of the most popular commercial network vulnerability scanners developed by Tenable Network Security. It is designed to automate the testing and discovery of known vulnerabilities before a hacker takes advantage of them. It also suggests solutions for the vulnerabilities identified during the scan. The Nessus vulnerability scanner products are annual subscription-based products. Luckily, the home version is free of charge, and it also offers plenty of tools to help explore your home network.

Nessus has countless capabilities and is fairly complex. We will download the free home version, and cover only the basics of its setup and configuration, as well as creating a scan and reading the report. You can get the detailed installation and user manual from the Tenable website.

Download the latest version of Nessus (appropriate to your operating system) from its download page (https://www.tenable.com/products/nessus/select-your-operating-system). In our example, I downloaded 64-bit Microsoft Windows version Nessus-7.0.0-x64.msi. Just double-click on the downloaded executable installation file and follow the instructions along the way.

Nessus uses a web interface to set up, scan, and view reports. After the installation, Nessus will load a page in your web browser to establish the initial settings, as shown in Figure 2. Click on Connect via SSL icon. Your browser will display an error indicating that the connection is not trusted or is unsecured. For the first connection, accept the certificate to continue configuration. The next screen (Figure 3) will be about creating your user account for the Nessus server. Create your Nessus System Administrator account with a Username * and Password * that you will define, and will use in the future every time you log in and then click on the Continue button. On the third screen (Figure 4), choose Home, Professional or Manager from the drop-down menu:

After that, go to https://www.tenable.com/products/nessus-home in a different tab and register for the activation code, as shown in Figure 2:

Your activation code will be sent to your email address. Type your activation code in the Activation Code box. After registration, Nessus will start downloading plugins from Tenable (Figure 2-2). This may take several minutes depending on your connection speed.

Once the plugins have been downloaded and compiled, the Nessus web UI will initialize and the Nessus server will start, as shown in Figure 3:

To create a scan, click on the New Scan icon in the upper-right corner. The Scan Templates page will appear, as shown in Figure 5:

You can choose any template listed on the Scan Templates page. We will choose Basic Network Scan for our test. The Basic Network Scan performs a full system scan that is suitable for any host. For example, you could use this template to perform an internal vulnerability scan on your organization's systems. As you choose Basic Network Scan, the Settings page will be launched, as shown in Figure 6.

Name your scan "TEST" and add a description. Enter IP scanning details on your home network. Keep in mind that Nessus Home allows you to scan up to 16 IP addresses per scanner. Save the configuration and on the next screen, click the Play button to launch the scan. Depending on how many devices you have on your network, the scan will take a while.

Once Nessus finishes scanning, click on the related scan; you'll see a bunch of color-coded graphs for each device on your network. Each color on the graph refers to different results, from information to the danger of a vulnerability, starting from the low level and ranging to critical. In Figure 7, we have three hosts (192.168.0.25, 192.168.0.1, and 192.168.0.11):

After the Nessus vulnerability scan, the results will be shown as displayed in Figure 8.

Click on any IP address to display the vulnerabilities found on the selected device, as shown in Figure 9. I chose 192.168.0.1 to see the details of the vulnerability scan:

When an individual vulnerability is selected, it displays more details of that particular vulnerability. My UPnP Internet Gateway Device (IGD) Protocol Detection vulnerability is shown in Figure 9. It gives lots of information about related details, such as the Description, Solution, Plugin Details, Risk Information, and Vulnerability Information:

Lastly, scan results can be saved in several different formats for reporting purposes. Click on the Export tab in the upper-right corner to pull down a menu with the formats Nessus, PDF, HTML, CSV, and Nessus DB:

In my case, I chose a PDF format and saved the vulnerability scan results. As shown in Figure 11, the report gives detailed information based on the IP addresses scanned. The Nessus scan report presents extensive data about the vulnerabilities detected on the networks. The report can be especially useful to security teams. They can use this report to identify vulnerabilities and the affected hosts in their network, and take the required action to mitigate vulnerabilities:

Nessus provides a lot of functionality and ability in one tool. Compared to other network scanning tools, it is fairly user-friendly, had easy-to-update plug-ins, and has nice reporting tools for upper management. Using this tool and seeing the vulnerabilities will help you gain knowledge of your systems, and also teach you how to protect them. New vulnerabilities are released almost daily, and in order to keep your systems consistently secure, you have to scan them regularly.

Keep in mind that finding the vulnerabilities before hackers take advantage of them is a great first step in keeping your systems safe.