Web Penetration Testing with Kali Linux

Chapter 1. Penetration Testing and Setup

Many organizations offer security services and use terms such as security audit, network or risk assessment, and Penetration Test with overlapping meanings. By definition, an audit is a measurable technical assessment of a system(s) or application(s). Security assessments are evaluations of risk, meaning services used to identify vulnerabilities in systems, applications, and processes.

Penetration Testing goes beyond an assessment by evaluating identified vulnerabilities to verify if the vulnerability is real or a false positive. For example, an audit or an assessment may utilize scanning tools that provide a few hundred possible vulnerabilities on multiple systems. A Penetration Test would attempt to attack those vulnerabilities in the same manner as a malicious hacker to verify which vulnerabilities are genuine reducing the real list of system vulnerabilities to a handful of security weaknesses. The most effective Penetration Tests are the ones that target a very specific system with a very specific goal. Quality over quantity is the true test of a successful Penetration Test. Enumerating a single system during a targeted attack reveals more about system security and response time to handle incidents than wide spectrum attack. By carefully choosing valuable targets, a Penetration Tester can determine the entire security infrastructure and associated risk for a valuable asset.

Note

Penetration Testing does not make networks more secure!

This is a common misinterpretation and should be clearly explained to all potential customers. Penetration Testing evaluates the effectiveness of existing security. If a customer does not have strong security then they will receive little value from Penetration Testing services. As a consultant, it is recommended that Penetration Testing services are offered as a means to verify security for existing systems once a customer believes they have exhausted all efforts to secure those systems and are ready to evaluate if there are any existing gaps in securing those systems.

Positioning a proper scope of work is critical when selling Penetration Testing services. The scope of work defines what systems and applications are being targeted as well as what toolsets may be used to compromise vulnerabilities that are found. Best practice is working with your customer during a design session to develop an acceptable scope of work that doesn't impact the value of the results.

Web Penetration Testing with Kali Linux—the next generation of BackTrack—is a hands-on guide that will provide you step-by-step methods for finding vulnerabilities and exploiting web applications. This book will cover researching targets, identifying and exploiting vulnerabilities in web applications as well as clients using web application services, defending web applications against common attacks, and building Penetration Testing deliverables for professional services practice. We believe this book is great for anyone who is interested in learning how to become a Penetration Tester, users who are new to Kali Linux and want to learn the features and differences in Kali versus BackTrack, and seasoned Penetration Testers who may need a refresher or reference on new tools and techniques.

This chapter will break down the fundamental concepts behind various security services as well as guidelines for building a professional Penetration Testing practice. Concepts include differentiating a Penetration Test from other services, methodology overview, and targeting web applications. This chapter also provides a brief overview of setting up a Kali Linux testing or real environment.

Web application Penetration Testing concepts

A web application is any application that uses a web browser as a client. This can be a simple message board or a very complex spreadsheet. Web applications are popular based on ease of access to services and centralized management of a system used by multiple parties. Requirements for accessing a web application can follow industry web browser client standards simplifying expectations from both the service providers as well as the hosts accessing the application.

Web applications are the most widely used type of applications within any organization. They are the standard for most Internet-based applications. If you look at smartphones and tablets, you will find that most applications on these devices are also web applications. This has created a new and large target-rich surface for security professionals as well as attackers exploiting those systems.

Penetration Testing web applications can vary in scope since there is a vast number of system types and business use cases for web application services. The core web application tiers which are hosting servers, accessing devices, and data depository should be tested along with communication between the tiers during a web application Penetration Testing exercise.

An example for developing a scope for a web application Penetration Test is testing a Linux server hosting applications for mobile devices. The scope of work at a minimum should include evaluating the Linux server (operating system, network configuration, and so on), applications hosted from the server, how systems and users authenticate, client devices accessing the server and communication between all three tiers. Additional areas of evaluation that could be included in the scope of work are how devices are obtained by employees, how devices are used outside of accessing the application, the surrounding network(s), maintenance of the systems, and the users of the systems. Some examples of why these other areas of scope matter are having the Linux server compromised by permitting connection from a mobile device infected by other means or obtaining an authorized mobile device through social media to capture confidential information.

We have included templates for scoping a web application penetration in Chapter 8, Penetration Test Executive Report. Some deliverable examples in this chapter offer checkbox surveys that can assist with walking a customer through possible targets for a web application Penetration Testing scope of work. Every scope of work should be customized around your customer's business objectives, expected timeframe of performance, allocated funds, and desired outcome. As stated before, templates serve as tools to enhance a design session for developing a scope of work.

Penetration Testing methodology

There are logical steps recommended for performing a Penetration Test. The first step is identifying the project's starting status. The most common terminology defining the starting state is Black box testing, White box testing, or a blend between White and Black box testing known as Gray box testing.

Black box assumes the Penetration Tester has no prior knowledge of the target network, company processes, or services it provides. Starting a Black box project requires a lot of reconnaissance and, typically, is a longer engagement based on the concept that real-world attackers can spend long durations of time studying targets before launching attacks.

As a security professional, we find Black box testing presents some problems when scoping a Penetration Test. Depending on the system and your familiarity with the environment, it can be difficult to estimate how long the reconnaissance phase will last. This usually presents a billing problem. Customers, in most cases, are not willing to write a blank cheque for you to spend unlimited time and resources on the reconnaissance phase; however, if you do not spend the time needed then your Penetration Test is over before it began. It is also unrealistic because a motivated attacker will not necessarily have the same scoping and billing restrictions as a professional Penetration Tester. That is why we recommend Gray box over Black box testing.

White box is when a Penetration Tester has intimate knowledge about the system. The goals of the Penetration Test are clearly defined and the outcome of the report from the test is usually expected. The tester has been provided with details on the target such as network information, type of systems, company processes, and services. White box testing typically is focused on a particular business objective such as meeting a compliance need, rather than generic assessment, and could be a shorter engagement depending on how the target space is limited. White box assignments could reduce information gathering efforts, such as reconnaissance services, equaling less cost for Penetration Testing services.

Note

An internal security group usually performs white box testing.

Gray box testing falls in between Black and White box testing. It is when the client or system owner agrees that some unknown information will eventually be discovered during a Reconnaissance phase, but allows the Penetration Tester to skip this part. The Penetration Tester is provided some basic details of the target; however, internal workings and some other privileged information is still kept from the Penetration Tester.

Real attackers tend to have some information about a target prior to engaging the target. Most attackers (with the exception of script kiddies or individuals downloading tools and running them) do not choose random targets. They are motivated and have usually interacted in some way with their target before attempting an attack. Gray box is an attractive choice approach for many security professionals conducting Penetration Tests because it mimics real-world approaches used by attackers and focuses on vulnerabilities rather than reconnaissance.

The scope of work defines how penetration services will be started and executed. Kicking off a Penetration Testing service engagement should include an information gathering session used to document the target environment and define the boundaries of the assignment to avoid unnecessary reconnaissance services or attacking systems that are out of scope. A well-defined scope of work will save a service provider from scope creep (defined as uncontrolled changes or continuous growth in a project's scope), operate within the expected timeframe and help provide more accurate deliverable upon concluding services.

Real attackers do not have boundaries such as time, funding, ethics, or tools meaning that limiting a Penetration Testing scope may not represent a real-world scenario. In contrast to a limited scope, having an unlimited scope may never evaluate critical vulnerabilities if a Penetration Test is concluded prior to attacking desired systems. For example, a Penetration Tester may capture user credentials to critical systems and conclude with accessing those systems without testing how vulnerable those systems are to network-based attacks. It's also important to include who is aware of the Penetration Test as a part of the scope. Real attackers may strike at anytime and probably when people are least expecting it.

Some fundamentals for developing a scope of work for a Penetration Test are as follows:

Definition of Target System(s): This specifies what systems should be tested. This includes the location on the network, types of systems, and business use of those systems.
Timeframe of Work Performed: When the testing should start and what is the timeframe provided to meet specified goals. Best practice is NOT to limit the time scope to business hours.
How Targets Are Evaluated: What types of testing methods such as scanning or exploitation are and not permitted? What is the risk associated with permitted specific testing methods? What is the impact of targets that become inoperable due to penetration attempts? Examples are; using social networking by pretending to be an employee, denial of service attack on key systems, or executing scripts on vulnerable servers. Some attack methods may pose a higher risk of damaging systems than others.
Tools and software: What tools and software are used during the Penetration Test? This is important and a little controversial. Many security professionals believe if they disclose their tools they will be giving away their secret sauce. We believe this is only the case when security professionals used widely available commercial products and are simply rebranding canned reports from these products. Seasoned security professionals will disclose the tools being used, and in some cases when vulnerabilities are exploited, documentation on the commands used within the tools to exploit a vulnerability. This makes the exploit re-creatable, and allows the client to truly understand how the system was compromised and the difficulty associated with the exploit.
Notified Parties: Who is aware of the Penetration Test? Are they briefed beforehand and able to prepare? Is reaction to penetration efforts part of the scope being tested? If so, it may make sense not to inform the security operations team prior to the Penetration Test. This is very important when looking at web applications that may be hosted by another party such as a cloud service provider that could be impacted from your services.
Initial Access Level: What type of information and access is provided prior to kicking off the Penetration Test? Does the Penetration Tester have access to the server via Internet and/or Intranet? What type of initial account level access is granted? Is this a Black, White, or Gray box assignment for each target?
Definition of Target Space: This defines the specific business functions included in the Penetration Test. For example, conducting a Penetration Test on a specific web application used by sales while not touching a different application hosted from the same server.
Identification of Critical Operation Areas: Define systems that should not be touched to avoid a negative impact from the Penetration Testing services. Is the active authentication server off limits? It's important to make critical assets clear prior to engaging a target.
Definition of the Flag: It is important to define how far a Penetration Test should compromise a system or a process. Should data be removed from the network or should the attacker just obtain a specific level of unauthorized access?
Deliverable: What type of final report is expected? What goals does the client specify to be accomplished upon closing a Penetration Testing service agreement? Make sure the goals are not open-ended to avoid scope creep of expected service. Is any of the data classified or designated for a specific group of people? How should the final report be delivered? It is important to deliver a sample report or periodic updates so that there are no surprises in the final report.
Remediation expectations: Are vulnerabilities expected to be documented with possible remediation action items? Who should be notified if a system is rendered unusable during a Penetration Testing exercise? What happens if sensitive data is discovered? Most Penetration Testing services do NOT include remediation of problems found.

Some service definitions that should be used to define the scope of services are:

Security Audit: Evaluating a system or an application's risk level against a set of standards or baselines. Standards are mandatory rules while baselines are the minimal acceptable level of security. Standards and baselines achieve consistency in security implementations and can be specific to industries, technologies, and processes.
Most requests for security serves for audits are focused on passing an official audit (for example preparing for a corporate or a government audit) or proving the baseline requirements are met for a mandatory set of regulations (for example following the HIPAA and HITECH mandates for protecting healthcare records). It is important to inform potential customers if your audit services include any level of insurance or protection if an audit isn't successful after your services. It's also critical to document the type of remediation included with audit services (that is, whether you would identify a problem, offer a remediation action plan or fix the problem). Auditing for compliance is much more than running a security tool. It relies heavily on the standard types of reporting and following a methodology that is an accepted standard for the audit.
In many cases, security audits give customers a false sense of security depending on what standards or baselines are being audited. Most standards and baselines have a long update process that is unable to keep up with the rapid changes in threats found in today's cyber world. It is HIGHLY recommended to offer security services beyond standards and baselines to raise the level of security to an acceptable level of protection for real-world threats. Services should include following up with customers to assist with remediation along with raising the bar for security beyond any industry standards and baselines.
Vulnerability Assessment: This is the process in which network devices, operating systems and application software are scanned in order to identify the presence of known and unknown vulnerabilities. Vulnerability is a gap, error, or weakness in how a system is designed, used, and protected. When a vulnerability is exploited, it can result in giving unauthorized access, escalation of privileges, denial-of-service to the asset, or other outcomes.
Vulnerability Assessments typically stop once a vulnerability is found, meaning that the Penetration Tester doesn't execute an attack against the vulnerability to verify if it's genuine. A Vulnerability Assessment deliverable provides potential risk associated with all the vulnerabilities found with possible remediation steps. There are many solutions such as Kali Linux that can be used to scan for vulnerabilities based on system/server type, operating system, ports open for communication and other means. Vulnerability Assessments can be White, Gray, or Black box depending on the nature of the assignment.
Vulnerability scans are only useful if they calculate risk. The downside of many security audits is vulnerability scan results that make security audits thicker without providing any real value. Many vulnerability scanners have false positives or identify vulnerabilities that are not really there. They do this because they incorrectly identify the OS or are looking for specific patches to fix vulnerabilities but not looking at rollup patches (patches that contain multiple smaller patches) or software revisions. Assigning risk to vulnerabilities gives a true definition and sense of how vulnerable a system is. In many cases, this means that vulnerability reports by automated tools will need to be checked.
Customers will want to know the risk associated with vulnerability and expected cost to reduce any risk found. To provide the value of cost, it's important to understand how to calculate risk.

Calculating risk

It is important to understand how to calculate risk associated with vulnerabilities found, so that a decision can be made on how to react. Most customers look to the CISSP triangle of CIA when determining the impact of risk. CIA is the confidentiality, integrity, and availability of a particular system or application. When determining the impact of risk, customers must look at each component individually as well as the vulnerability in its entirety to gain a true perspective of the risk and determine the likelihood of impact.

It is up to the customer to decide if the risk associated to vulnerability found justifies or outweighs the cost of controls required to reduce the risk to an acceptable level. A customer may not be able to spend a million dollars on remediating a threat that compromises guest printers; however, they will be very willing to spend twice as much on protecting systems with the company's confidential data.

The Certified Information Systems Security Professional (CISSP) curriculum lists formulas for calculating risk as follow.

A Single Loss Expectancy (SLE) is the cost of a single loss to an Asset Value (AV). Exposure Factor (EF) is the impact the loss of the asset will have to an organization such as loss of revenue due to an Internet-facing server shutting down. Customers should calculate the SLE of an asset when evaluating security investments to help identify the level of funding that should be assigned for controls. If a SLE would cause a million dollars of damage to the company, it would make sense to consider that in the budget.

The Single Loss Expectancy formula:

SLE = AV * EF

The next important formula is identifying how often the SLE could occur. If an SLE worth a million dollars could happen once in a million years, such as a meteor falling out of the sky, it may not be worth investing millions in a protection dome around your headquarters. In contrast, if a fire could cause a million dollars worth of damage and is expected every couple of years, it would be wise to invest in a fire prevention system. The number of times an asset is lost is called the Annual Rate of Occurrence (ARO).

The Annualized Loss Expectancy (ALE) is an expression of annual anticipated loss due to risk. For example, a meteor falling has a very low annualized expectancy (once in a million years), while a fire is a lot more likely and should be calculated in future investments for protecting a building.

Annualized Loss Expectancy formula:

ALE = SLE * ARO

The final and important question to answer is the risk associated with an asset used to figure out the investment for controls. This can determine if and how much the customer should invest into remediating vulnerability found in a asset.

Risk formula:

Risk = Asset Value * Threat * Vulnerability * Impact

It is common for customers not to have values for variables in Risk Management formulas. These formulas serve as guidance systems, to help the customer better understand how they should invest in security. In my previous examples, using the formulas with estimated values for a meteor shower and fire in a building, should help explain with estimated dollar value why a fire prevention system is a better investment than metal dome protecting from falling objects.

Penetration Testing is the method of attacking system vulnerabilities in a similar way to real malicious attackers. Typically, Penetration Testing services are requested when a system or network has exhausted investments in security and clients are seeking to verify if all avenues of security have been covered. Penetration Testing can be Black, White, or Gray box depending on the scope of work agreed upon.

The key difference between a Penetration Test and Vulnerability Assessment is that a Penetration Test will act upon vulnerabilities found and verify if they are real reducing the list of confirmed risk associated with a target. A Vulnerability Assessment of a target could change to a Penetration Test once the asset owner has authorized the service provider to execute attacks against the vulnerabilities identified in a target. Typically, Penetration Testing services have a higher cost associated since the services require more expensive resources, tools, and time to successfully complete assignments. One popular misconception is that a Penetration Testing service enhances IT security since services have a higher cost associated than other security services:

Penetration Testing does not make IT networks more secure, since services evaluate existing security! A customer should not consider a Penetration Test if there is a belief the target is not completely secure.
Penetration Testing can cause a negative impact to systems: It's critical to have authorization in writing from the proper authorities before starting a Penetration Test of an asset owned by another party. Not having proper authorization could be seen as illegal hacking by authorities. Authorization should include who is liable for any damages caused during a penetration exercise as well as who should be contacted to avoid future negative impacts once a system is damaged. Best practice is alerting the customers of all the potential risks associated with each method used to compromise a target prior to executing the attack to level set expectations. This is also one of the reasons we recommend targeted Penetration Testing with a small scope. It is easier to be much more methodical in your approach. As a common best practice, we receive confirmation, which is a worst case scenario, that a system can be restored by a customer using backups or some other disaster recovery method.

Penetration Testing deliverable expectations should be well defined while agreeing on a scope of work. The most common methods by which hackers obtain information about targets is through social engineering via attacking people rather than systems. Examples are interviewing for a position within the organization and walking out a week later with sensitive data offered without resistance. This type of deliverable may not be acceptable if a customer is interested in knowing how vulnerable their web applications are to remote attack. It is also important to have a defined end-goal so that all parties understand when the penetration services are considered concluded. Usually, an agreed-upon deliverable serves this purpose.

A Penetration Testing engagement's success for a service provider is based on profitability of time and services used to deliver the Penetration Testing engagement. A more efficient and accurate process means better results for less services used. The higher the quality of the deliverables, the closer the service can meet customer expectation, resulting in a better reputation and more future business. For these reasons, it's important to develop a methodology for executing Penetration Testing services as well as for how to report what is found.

Kali Penetration Testing concepts

Kali Linux is designed to follow the flow of a Penetration Testing service engagement. Regardless if the starting point is White, Black, or Gray box testing, there is a set of steps that should be followed when Penetration Testing a target with Kali or other tools.

Step 1 – Reconnaissance

You should learn as much as possible about a target's environment and system traits prior to launching an attack. The more information you can identify about a target, the better chance you have to identify the easiest and fastest path to success. Black box testing requires more reconnaissance than White box testing since data is not provided about the target(s). Reconnaissance services can include researching a target's Internet footprint, monitoring resources, people, and processes, scanning for network information such as IP addresses and systems types, social engineering public services such as help desk and other means.

Reconnaissance is the first step of a Penetration Testing service engagement regardless if you are verifying known information or seeking new intelligence on a target. Reconnaissance begins by defining the target environment based on the scope of work. Once the target is identified, research is performed to gather intelligence on the target such as what ports are used for communication, where it is hosted, the type of services being offered to clients, and so on. This data will develop a plan of action regarding the easiest methods to obtain desired results. The deliverable of a reconnaissance assignment should include a list of all the assets being targeted, what applications are associated with the assets, services used, and possible asset owners.

Kali Linux offers a category labeled Information Gathering that serves as a Reconnaissance resource. Tools include methods to research network, data center, wireless, and host systems.

The following is the list of Reconnaissance goals:

Identify target(s)
Define applications and business use
Identify system types
Identify available ports
Identify running services
Passively social engineer information
Document findings

Step 2 – Target evaluation

Once a target is identified and researched from Reconnaissance efforts, the next step is evaluating the target for vulnerabilities. At this point, the Penetration Tester should know enough about a target to select how to analyze for possible vulnerabilities or weakness. Examples for testing for weakness in how the web application operates, identified services, communication ports, or other means. Vulnerability Assessments and Security Audits typically conclude after this phase of the target evaluation process.

Capturing detailed information through Reconnaissance improves accuracy of targeting possible vulnerabilities, shortens execution time to perform target evaluation services, and helps to avoid existing security. For example, running a generic vulnerability scanner against a web application server would probably alert the asset owner, take a while to execute and only generate generic details about the system and applications. Scanning a server for a specific vulnerability based on data obtained from Reconnaissance would be harder for the asset owner to detect, provide a good possible vulnerability to exploit, and take seconds to execute.

Evaluating targets for vulnerabilities could be manual or automated through tools. There is a range of tools offered in Kali Linux grouped as a category labeled Vulnerability Analysis. Tools range from assessing network devices to databases.

The following is the list of Target Evaluation goals:

Evaluation targets for weakness
Identify and prioritize vulnerable systems
Map vulnerable systems to asset owners
Document findings

Step 3 – Exploitation

This step exploits vulnerabilities found to verify if the vulnerabilities are real and what possible information or access can be obtained. Exploitation separates Penetration Testing services from passive services such as Vulnerability Assessments and Audits. Exploitation and all the following steps have legal ramifications without authorization from the asset owners of the target.

The success of this step is heavily dependent on previous efforts. Most exploits are developed for specific vulnerabilities and can cause undesired consequences if executed incorrectly. Best practice is identifying a handful of vulnerabilities and developing an attack strategy based on leading with the most vulnerable first.

Exploiting targets can be manual or automated depending on the end objective. Some examples are running SQL Injections to gain admin access to a web application or social engineering a Helpdesk person into providing admin login credentials. Kali Linux offers a dedicated catalog of tools titled Exploitation Tools for exploiting targets that range from exploiting specific services to social engineering packages.

The following is the list of Exploitation goals:

Exploit vulnerabilities
Obtain foothold
Capture unauthorized data
Aggressively social engineer
Attack other systems or applications
Document findings

Step 4 – Privilege Escalation

Having access to a target does not guarantee accomplishing the goal of a penetration assignment. In many cases, exploiting a vulnerable system may only give limited access to a target's data and resources. The attacker must escalate privileges granted to gain the access required to capture the flag, which could be sensitive data, critical infrastructure, and so on.

Privilege Escalation can include identifying and cracking passwords, user accounts, and unauthorized IT space. An example is achieving limited user access, identifying a shadow file containing administration login credentials, obtaining an administrator password through password cracking, and accessing internal application systems with administrator access rights.

Kali Linux includes a number of tools that can help gain Privilege Escalation through the Password Attacks and Exploitation Tools catalog. Since most of these tools include methods to obtain initial access and Privilege Escalation, they are gathered and grouped according to their toolsets.

The following is a list of Privilege Escalation goals:

Obtain escalated level access to system(s) and network(s)
Uncover other user account information
Access other systems with escalated privileges
Document findings

Step 5 – maintaining a foothold

The final step is maintaining access by establishing other entry points into the target and, if possible, covering evidence of the penetration. It is possible that penetration efforts will trigger defenses that will eventually secure how the Penetration Tester obtained access to the network. Best practice is establishing other means to access the target as insurance against the primary path being closed. Alternative access methods could be backdoors, new administration accounts, encrypted tunnels, and new network access channels.

The other important aspect of maintaining a foothold in a target is removing evidence of the penetration. This will make it harder to detect the attack thus reducing the reaction by security defenses. Removing evidence includes erasing user logs, masking existing access channels, and removing the traces of tampering such as error messages caused by penetration efforts.

Kali Linux includes a catalog titled Maintaining Access focused on keeping a foothold within a target. Tools are used for establishing various forms of backdoors into a target.

The following is a list of goals for maintaining a foothold:

Establish multiple access methods to target network
Remove evidence of authorized access
Repair systems impacting by exploitation
Inject false data if needed
Hide communication methods through encryption and other means
Document findings

Kali system setup

Kali Linux can be downloaded in a few different ways. One of the most popular ways to get Kali Linux is to download the ISO image. The ISO image is available in 32-bit and 64-bit images.

If you plan on using Kali Linux on a virtual machine such as VMware, there is a VM image prebuilt. The advantage of downloading the VM image is that it comes preloaded with VMware tools. The VM image is a 32-bit image with Physical Address Extension support, or better known as PAE. In theory, a PAE kernel allows the system to access more system memory than a traditional 32-bit operating system. There have been some well-known personalities in the world of operating systems that have argued for and against the usefulness of a PAE kernel. However, the authors of this book suggest using the VM image of Kali Linux if you plan on using it in a virtual environment.

Running Kali Linux from external media

Kali Linux can be run without installing software on a host hard drive by accessing it from an external media source such as a USB drive or DVD. This method is simple to enable; however, it has performance and operational implementations. Kali Linux having to load programs from a remote source would impact performance and some applications or hardware settings may not operate properly. Using read-only storage media does not permit saving custom settings that may be required to make Kali Linux operate correctly. It's highly recommended to install Kali Linux on a host hard drive.

Installing Kali Linux

Installing Kali Linux on your computer is straightforward and similar to installing other operating systems. First, you'll need compatible computer hardware. Kali is supported on i386, amd64, and ARM (both armel and armhf) platforms. The hardware requirements are shown in the following list, although we suggest exceeding the minimum amount by at least three times. Kali Linux, in general, will perform better if it has access to more RAM and is installed on newer machines. Download Kali Linux and either burn the ISO to DVD, or prepare a USB stick with Kali Linux Live as the installation medium. If you do not have a DVD drive or a USB port on your computer, check out the Kali Linux Network Install.

The following is a list of minimum installation requirements:

A minimum of 8 GB disk space for installing Kali Linux.
For i386 and amd64 architectures, a minimum of 512MB RAM.
CD-DVD Drive / USB boot support.
You will also need an active Internet connection before installation. This is very important or you will not be able to configure and access repositories during installation.
1. When you start Kali you will be presented with a Boot Install screen. You may choose what type of installation (GUI-based or text-based) you would like to perform.
2. Select the local language preference, country, and keyboard preferences.
3. Select a hostname for the Kali Linux host. The default hostname is Kali.
4. Select a password. Simple passwords may not work so chose something that has some degree of complexity.
5. The next prompt asks for your timezone. Modify accordingly and select Continue. The next screenshot shows selecting Eastern standard time.
  The installer will ask to set up your partitions. If you are installing Kali on a virtual image, select Guided Install – Whole Disk. This will destroy all data on the disk and install Kali Linux. Keep in mind that on a virtual machine, only the virtual disk is getting destroyed. Advanced users can select manual configurations to customize partitions. Kali also offers the option of using LVM, logical volume manager. LVM allows you to manage and resize partitions after installation. In theory, it is supposed to allow flexibility when storage needs change from initial installation. However, unless your Kali Linux needs are extremely complex, you most likely will not need to use it.
6. The last window displays a review of the installation settings. If everything looks correct, select Yes to continue the process as shown in the following screenshot:
7. Kali Linux uses central repositories to distribute application packages. If you would like to install these packages, you need to use a network mirror. The packages are downloaded via HTTP protocol. If your network uses a proxy server, you will also need to configure the proxy settings for you network.
8. Kali will prompt to install GRUB. GRUB is a multi-bootloader that gives the user the ability to pick and boot up to multiple operating systems. In almost all cases, you should select to install GRUB. If you are configuring your system to dual boot, you will want to make sure GRUB recognizes the other operating systems in order for it to give users the options to boot into an alternative operating system. If it does not detect any other operating systems, the machine will automatically boot into Kali Linux.
9. Congratulations! You have finished installing Kali Linux. You will want to remove all media (physical or virtual) and select Continue to reboot your system.

Kali Linux and VM image first run

On some Kali installation methods, you will be asked to set the root's password. When Kali Linux boots up, enter the root's username and the password you selected. If you downloaded a VM image of Kali, you will need the root password. The default username is root and password is toor.

Kali toolset overview

Kali Linux offers a number of customized tools designed for Penetration Testing. Tools are categorized in the following groups as seen in the drop-down menu shown in the following screenshot:

Information Gathering: These are Reconnaissance tools used to gather data on your target network and devices. Tools range from identifying devices to protocols used.
Vulnerability Analysis: Tools from this section focus on evaluating systems for vulnerabilities. Typically, these are run against systems found using the Information Gathering Reconnaissance tools.
Web Applications: These are tools used to audit and exploit vulnerabilities in web servers. Many of the audit tools we will refer to in this book come directly from this category. However web applications do not always refer to attacks against web servers, they can simply be web-based tools for networking services. For example, web proxies will be found under this section.
Password Attacks: This section of tools primarily deals with brute force or the offline computation of passwords or shared keys used for authentication.
Wireless Attacks: These are tools used to exploit vulnerabilities found in wireless protocols. 802.11 tools will be found here, including tools such as aircrack, airmon, and wireless password cracking tools. In addition, this section has tools related to RFID and Bluetooth vulnerabilities as well. In many cases, the tools in this section will need to be used with a wireless adapter that can be configured by Kali to be put in promiscuous mode.
Exploitation Tools: These are tools used to exploit vulnerabilities found in systems. Usually, a vulnerability is identified during a Vulnerability Assessment of a target.
Sniffing and Spoofing: These are tools used for network packet captures, network packet manipulators, packet crafting applications, and web spoofing. There are also a few VoIP reconstruction applications.
Maintaining Access: Maintaining Access tools are used once a foothold is established into a target system or network. It is common to find compromised systems having multiple hooks back to the attacker to provide alternative routes in the event a vulnerability that is used by the attacker is found and remediated.
Reverse Engineering: These tools are used to disable an executable and debug programs. The purpose of reverse engineering is analyzing how a program was developed so it can be copied, modified, or lead to development of other programs. Reverse Engineering is also used for malware analysis to determine what an executable does or by researchers to attempt to find vulnerabilities in software applications.
Stress Testing: Stress Testing tools are used to evaluate how much data a system can handle. Undesired outcomes could be obtained from overloading systems such as causing a device controlling network communication to open all communication channels or a system shutting down (also known as a denial of service attack).
Hardware Hacking: This section contains Android tools, which could be classified as mobile, and Ardunio tools that are used for programming and controlling other small electronic devices.
Forensics: Forensics tools are used to monitor and analyze computer network traffic and applications.
Reporting Tools: Reporting tools are methods to deliver information found during a penetration exercise.
System Services: This is where you can enable and disable Kali services. Services are grouped into BeEF, Dradis, HTTP, Metasploit, MySQL, and SSH.

Note

There are other tools included in the Kali Linux build such as web browsers, quick links to tune how the Kali Linux build is seen on the network, search tools, and other useful applications.