You're reading from The Ultimate Kali Linux Book - Second Edition

Product typeBook

Published inFeb 2022

PublisherPackt

ISBN-139781801818933

Edition2nd Edition

Concepts

Cybersecurity

Author (1)

Glen D. Singh

Chapter 6: Performing Vulnerability Assessments

As you have learned so far, the information-gathering phase is vital for later phases of penetration testing as a cybersecurity professional. Discovering security vulnerabilities means having to focus on understanding the attack surface of your target. The attack surface is defined as all the points of entry into a system or network that a threat actor, such as a hacker, can exploit and compromise the system based on the number of security vulnerabilities that exist. As an aspiring ethical hacker and penetration tester, understanding the number of security flaws and their level of severity can help you understand which systems are easier to compromise on a network than others.

In this chapter, you will learn how to use Kali Linux with various popular tools to perform a vulnerability assessment on a network. You will start by learning how to install, perform, and analyze scan results using Nessus, one of the most popular and industry...

Technical requirements

To follow along with the exercises in this chapter, please ensure that you have met the following hardware and software requirements:

Kali Linux 2021.2: https://www.kali.org/get-kali/
Nessus: https://www.tenable.com/products/nessus/nessus-essentials
Greenbone Vulnerability Manager: https://github.com/greenbone/gvmd

Nessus and its policies

When diving into the field of cybersecurity, there is a very well-known tool everyone needs to know about, and that's Nessus. Nessus is a vulnerability scanner that can detect over 47,000 Common Vulnerability and Exposure (CVE) security flaws on systems. Furthermore, Nessus allows security professionals to deploy Nessus within centralized locations and automate periodic scanning on systems, which allows continuous and automated vulnerability assessment within an organization.

As an aspiring penetration tester, you may need to use Nessus to perform a vulnerability assessment within an organization, determine the risk and severity of each security flaw, and provide recommendations on how to mitigate the risk of possible cyber attacks based on the security vulnerabilities found. In this section, you will learn how to set up and perform a vulnerability assessment using Nessus on your Kali Linux machine.

Setting up Nessus

In this section, you will...

Vulnerability discovery using Nmap

The Nmap Scripting Engine (NSE) is one of the most powerful features within Nmap. It allows penetration testers and security researchers to create, automate, and perform customized scanning on a target system or network. When using NSE, the scanning techniques are usually aggressive and can sometimes create data loss or even crash a target system. However, NSE allows a penetration tester to easily identify security vulnerabilities and whether the target is exploitable.

The following are various categories of scripts within NSE:

Auth: This category contains scripts that can scan a target to detect whether authentication bypass is possible.
Broadcast: This category contains scripts that are used to discover host systems on a network.
Brute: This category contains scripts that are used to perform some types of brute-force attacks on a remote server to gain unauthorized access.
Default: This category contains a set of default...

Working with Greenbone Vulnerability Manager

The Open Vulnerability Assessment Scanner (OpenVAS) tool is a free vulnerability scanner that allows both ethical hackers and penetration testers to perform a vulnerability assessment on a network. OpenVAS can scan both authenticated and unauthenticated vulnerability assets within an organization. When using an authenticated scan, the penetration tester provides valid login credentials to the vulnerability scanner, which allows it to authenticate to a system to provide a thorough scan for any misconfigurations on the target system's settings. However, the unauthenticated scan is usually not as thorough since it looks for any security vulnerabilities on the surface of the target and provides a report.

Greenbone Vulnerability Manager (GVM) is a centralized management tool that manages the functions and vulnerabilities of OpenVAS. In this exercise, you will learn how to set up GVM on Kali Linux and perform a vulnerability assessment...

Using web application scanners

As a penetration tester, you will also be required to perform web application security testing based on the scope of your penetration testing engagements. In this section, you will learn how to use various types of web application scanners to identify and fingerprint web applications on a target server.

Before proceeding, make sure you use the following guidelines to ensure you get the same results:

During the next few sections, the target systems will be Metasploitable 2 and OWASP BWA virtual machines.
Ensure Kali Linux has end-to-end connectivity with the Metasploitable 2 and OWASP BWA systems.

Let's get started!

WhatWeb

WhatWeb is a tool that is used to help penetration testers easily identify the available technologies and fingerprint web servers and web applications on a target system. WhatWeb is also pre-installed within Kali Linux and should be part of your arsenal of tools to help you on your journey.

To profile...

Summary

In this chapter, you learned about the importance of discovering security vulnerabilities within an organization and its assets. You also gained hands-on experience and skills with using various tools such as Nessus, Nmap, and Metasploit to perform security assessments on systems. You also discovered how various tools and techniques can be used to easily identify security flaws on web applications.

I hope this chapter has been informative for you and will prove helpful in your journey as an aspiring penetration tester, learning how to simulate real-world cyberattacks to discover security vulnerabilities and perform exploitation using Kali Linux. In the next chapter, Chapter 7, Understanding Network Penetration Testing, we will focus on how to use various techniques and strategies when performing network penetration testing.

Glen D. Singh is a cybersecurity author, educator and SecOps professional. His areas of expertise are cybersecurity operations, offensive security tactics and techniques, and enterprise networking. He holds a Master of Science (MSc) in cybersecurity and many industry certifications from top awarding bodies such as EC-Council, Cisco, and Check Point. Glen loves teaching and mentoring others while sharing his wealth of knowledge and experience as an author. He has written many books, which focus on vulnerability discovery and exploitation, threat detection, intrusion analysis, incident response, network security, and enterprise networking. As an aspiring game changer, Glen is passionate about increasing cybersecurity awareness in his homeland, Trinidad and Tobago.
Read more about Glen D. Singh

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