How to Hack a WPA Wireless Network (Wifi) using Aircrack-ng and John the Ripper

Here is a video tutorial I created showing how easy it is to hack a wireless network using WPA keys for their security. It's a short 12 minute video and I hope you find it not only instructional, but also liberating. After all, informed people make the best decisions.

John the Ripper (JtR) cracks passwords offline. That is, "incorrect number of passwords entered limit" does not affect  JtR. As you can see in the video, using aireplay-ng, fake deauthentication packets were injected to the wireless access point  to force all users to reauthenticate (without them knowing it). During reauthentication, the WPA keys are exchanged between the client and the wireless access point. This exchange was recorded into a file "wificrack.cap" and the hashed PSK (Pre-Shared Key) was then cracked using JtR.  In the video, you can also see that the output file of airodump-ng can be opened using Wireshark. Opening the cap file with Wireshark reveals a lot of information about the clients connected to the wireless access point. For instance, we know the wireless AP is a Cisco-Li (Cisco-Linksys), and the WPA handshake captured was from an Apple device. The MAC address is even shown!

Freeing Disk Space in Kali Linux (Basic steps), Especially the apt-get Cache

Kali is a Debian-based Linux developed with penetration-testers in mind. Think of it as a toolbox. It is basically a Debian Linux, but with all the penetration testing tools installed, for free. This includes Metasploit, OpenVAS vulnerability scanners, exploitDB, Hydra, aircrack-ng, John the Ripper, etc. These come on top Linux's common formidable tools such as OpenSSH (for creating tunnels), netcat, and nmap to name a few. 

Since Kali is Debian, then the method used here do apply to any Debian-based Linux systems (+ Ubuntu). Although, since we are talking about Kali, which is usually ran as 'root', then most of the screenshots will show that the user is running the commands as root. If you are not logged in as root, just add the word 'sudo' in the beginning of every command. For example: instead of issueing command 'apt-get clean', type 'sudo apt-get clean'.

Let us assume, you get an error in your Kali Linux saying that you are running out of space. In the screenshot below, My Kali is running on Oracle VirtualBox with a dynamically allocated 15Gb of space. Technically I don't have to worry about disk space because the Virtual Disk will expand when needed. But I still want to free some space.  

You get an error that you are running on disk space. Kali

Step 1: Check Disk space and where you are consuming space the most. Use df -h. the '-h' option in df is to format the result in 'human-readable' format. 

df -h results show the entire disk is "full"