In this article by Juned A Ansari, author of the book, Web Penetration Testing with Kali Linux, Second Edition, the author wants us to learn about the following topics:

• Introduction to penetration testing
• An Overview of Kali Linux
• Using Tor for penetration testing

(For more resources related to this topic, see here.)

Introduction to penetration testing

Penetration testing or Ethical hacking is a proactive way of testing your web applications by simulating an attack that's similar to a real attack that could occur on any given day. We will use the tools provided in Kali Linux to accomplish this. Kali Linux is the rebranded version of Backtrack and is now based on Debian-derived Linux distribution. It comes preinstalled with a large list of popular hacking tools that are ready to use with all the prerequisites installed. We will dwell deep into the tools that would help Pentest web applications, and also attack websites in a lab vulnerable to major flaws found in real world web applications.

An Overview of Kali Linux

Kali Linux is security-focused Linux distribution based on Debian. It's a rebranded version of the famous Linux distribution known as Backtrack, which came with a huge repository of open source hacking tools for network, wireless, and web application penetration testing. Although Kali Linux contains most of the tools from Backtrack, the main aim of Kali Linux is to make it portable so that it can be installed on devices based on the ARM architectures, such as tablets and Chromebook, which makes the tools available at your disposal with much ease.

Using open source hacking tools comes with a major drawback. They contain a whole lot of dependencies when installed on Linux, and they need to be installed in a predefined sequence; authors of some tools have not released accurate documentation, which makes our life difficult.

Kali Linux simplifies this process; it contains many tools preinstalled with all the dependencies and are in ready-to-use condition so that you can pay more attention for the actual attack and not on installing the tool. Updates for tools installed in Kali Linux are more frequently released, which helps you to keep the tools up to date. A noncommercial toolkit that has all the major hacking tools preinstalled to test real-world networks and applications is a dream of every ethical hacker and the authors of Kali Linux make every effort to make our life easy, which enables us to spend more time on finding the actual flaws rather than building a toolkit.

Using Tor for penetration testing

The main aim of a penetration test is to hack into a web application in a way that a real-world malicious hacker would do it. Tor provides an interesting option to emulate the steps that a black hat hacker uses to protect his identity and location. Although an ethical hacker trying to improve the security of a web application should be not be concerned about hiding his location, Tor will give an additional option of testing the edge security systems such as network firewalls, web application firewalls, and IPS devices.

Black hat hackers try every method to protect their location and true identity; they do not use a permanent IP address and constantly change it to fool cybercrime investigators. You will find port scanning request from a different range of IP addresses, and the actual exploitation having the source IP address that you edge security systems are logging for the first time. With the necessary written approval from the client, you can use Tor to emulate an attacker by connecting to the web application from an unknown IP address that the system does not usually see connections from. Using Tor makes it more difficult to trace back the intrusion attempt to the actual attacker.

Tor uses a virtual circuit of interconnected network relays to bounce encrypted data packets. The encryption is multilayered and the final network relay releasing the data to the public Internet cannot identify the source of the communication as the entire packet was encrypted and only a part of it is decrypted at each node. The destination computer sees the final exit point of the data packet as the source of the communication, thus protecting the real identify and location of the user. The following figure shows the working of Tor:

Summary

This article served as an introduction to penetration testing of web application and Kali Linux. At the end, we looked at how to use Tor for penetration testing.

Resources for Article:

Further resources on this subject:

• An Introduction to WEP[article]
• WLAN Encryption Flaws[article]
• What is Kali Linux [article]