How to use Nessus (Scan for vunerabilities)

 

What is a Vulnerability scanner?

A vulnerability scanner is a computer program that is designed to assess computers, networks, or applications. They Scan for known weaknesses. These scanners are used to discover weaknesses of a given system. They are best for identifying and detecting vulnerabilities. These vulnerabilities can arise from misconfiguration or flawed programming within a network-based asset such as a firewall, router, web server, application server, etc. Modern scanners are available as SAAS (Software as a service). You can customize vulnerability reports as well as the installed software, open ports, certificates, and other host information that can be queried as part of its workflow.

Why Nessus?

Nessus is a vulnerability scanner that is very popular within the cybersecurity industry. It allows you to scan your environment/target (up to 16 free scans a month). Nessus has high speed, very detailed/in-depth assessments, and convenient in many ways.
The free version is an excellent tool to get started with. This product can be described as the industry standard of vulnerability scanners.
Although many different scanners exist, Nessus is one of the top dogs.

Sign up with Nessus (Free Version)

To get started, click the link below to take you to Tenable (The makers of Nessus).

https://www.tenable.com/products/nessus/nessus-essentials

Register on this page you will get an activation code sent to your email, activate your account to get started.

Once you are registered with nessus you can move onto the next step below.

Setting up Nessus

To get Nessus up and running you will need to log into your Kali Machine and run the following command.

/bin/systemctl start nessusd.service

Note: You might need to run ‘sudo’ before the command (and enter your password) depending on which user you are logged in as.

Once this is done you need to navigate to:

https://kali:8834/

You should be met by a screen that looks like this…

This can take a while to load up (especially on your first time) so be patient and wait till it is ready.

Once ready sign in with the username and password you created earlier.

Once this is all done get the IP address you want to run a vulnerability assessment on.

I am going to be using the ‘Delivery’ machine of www.hackthebox.eu as my target for this scan.

Ping the machine before you start the scan to check that you are connected

Once you have established a connection with your target we can start to confirgure the scan. (Remember you only get 16 free scans a month use these wisely)

Running a Scan (pew pew)

Nessus has so many different types of scans you can use. Since this is our first time let us just start with a Basic Network Scan. (Not as basic as it sounds)

A lot of settings exist that you can customize before sending a scan off.

Make sure that you have put the correct IP address/Domain into the targets field. You can give your scan a name and fill in a description if you wish to do so.
Some features are very cool, you can schedule a scan to start at a specific time. (This could be downtime/out-of-office hours at a company for example)

Set the results up to be sent to an email?

Your scan can be quick/complex. You can scan all ports, common ports, or just a specific custom set of port/s you like.

I am not going to go over every single feature of this scan in this blog, I have just named a few. For a more in-depth view please watch my youtube video on this.

Click on the scan to open it up, you can even do this while it is still running to check out the live results coming in!

Finishing up

Lovely, a successful scan! Now it is time to review the results and extract useful information. Nessus even categorizes the vulnerabilities into Critical, High, Medium, Low, Info (Information disclosure).
Don’t take these categories too literally, sometimes information disclosure is all we need to hack a system. So carefully review the results and look for known vulnerabilities in these areas. Nessus even tells you why/how parts a vulnerable.

Thank you for taking the time to read my blog. I hope this was useful to you. Please check out my youtube channel. Watch the video where I run through setting up Nessus and installing it. If you have not already.