A Powerful Vulnerabilty Scanner: Nessus- Part I

I will have some blog posts about Nessus. In this first one, I will mention general issues about it.

What is Nessus?

Nessus is a proprietary comprehensive vulnerability scanning software. It is free of charge for personal use in a non-enterprise environment. Its goal is to detect potential vulnerabilities on the tested systems.

You can scan ports and see the things crackers can find to hack so you can take action before they do! There will be some examples later for the vulnerabilities we can find with Nessus.

I always think Nessus is kind of outbox scanner for remote stuff and usually it works in that way. However, it can find default password or weak passwords too.

If you are working on a vulnerability management project, I will recommend you to have another scanner for scanning in the boxes ( i.e vulnerabilities for the software running on the machines. I like  Sunbelt Network Security Inspector for this purpose)

Anyway, let’s check License options for Nessus.

Licenses: What are Licenses? Wasn’t Nessus GPL and free ?

It was free but in 2005 creator of  Nessus sold it to Tenable Network Security. Tenable still maintains  Nessus 2.0 under GPL. They closed the source code for the version 3.0 and higher.

Version 3.0 was the first one which was done by Tenable. It was running almost 5 times faster than v2.  V3 was popular too but having 3 licenses for one product makes users a little confused.

The first type of the licenses is ProfessionalFeed License. With this license, Tenable provides you support of the application. They also provide plugins for you earlier than other licenses.

Pricing for the ProfessionalFeed is based upon the number of Nessus scanners in use within your organization, consultancy or service. The cost is $1,200 per scanner per year.

You can buy ProfessionalFeed from here.

The other type of License is HomeFeed License. A HomeFeed is available for free to individual home users, and cannot be used by organizations or individuals professionally.

The last one is on demand. It allows you to evaluate the ProfessionalFeed by using the HomeFeed subscription commercially for 15 days. You may only perform such an evaluation once.

The on-demand evaluation does not give you access to the customer portal, nor to the features specific to the ProfessionalFeed but should be adequate to test Nessus. You can obtain an activation code here.

Installing and Activating Nessus

Installing Nessus is so straight forward. You can download it from this link. It can run on Linux, Windows and Mac.

For this blog post, I installed it on a windows machine.

After you set it up, don’t forget to activate it. (Remember, even non-professional use of nessus, you are  required to get it activated. (They will send you activation key via e-mail, just grab the key and paste on the dialog window)

How It Works

You need to understand how the software works before scanning the machines across the network.

The most important thing you need to know is Nessus is agentless scanner. What is agentless?

Well, some security software needs to be installed on each machine you scan. However, the way nessus works is different. It uses client/server architecture. There will be a client machine in which you can run the software and make configuration for the scan. There will also be a server, the machine which performs what you tell by using the client machine.

Server and client can be same machine. Don’t forget, you don’t need to pay for each client but you need to pay for each server you install (They are required to have different licenses)

Client/Server Architecture brings some flexibilities. The first one is remote scanning.

You can install the server inside of the network and run client from a remote place say your home. This is so helpful since you don’t need to deal with firewall or IDS issues which can effect the scanning result.

Second advantage is one machine is enough to run a scan for all the network. This is definitely time saving!

I will cover the usage and configuration of Nessus in the next blog post.

One thought on “A Powerful Vulnerabilty Scanner: Nessus- Part I

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