The summary of the changelog since the 2021.3 release from September 2021 is: With the end of 2021 just around the corner, we are pushing out the last release of the year with Kali Linux 2021.4, which is ready for immediate download or updating. This was primarily added because the development team found they needed to do a lot of wireless assessments. Kali also has a custom built kernel tha is patched for injection. Kali Linux is developed in a secure location with only a small number of trusted people that are allowed to commit packages, with each package being signed by the developer. Most packages Kali uses are imported from the Debian repositories.

The third core developer Raphaël Hertzog joined them as Debian expert. It was developed by Mati Aharoni and Devon Kearns of Offensive Security through the rewrite of BackTrack, their previous forensics Linux distribution based on Ubuntu. It is a supported platform of the Metasploit Project's Metasploit Framework, a tool for developing and executing security exploits. Kali Linux can run natively when installed on a computer's hard disk, can be booted from a live CD or live USB, or it can run within a virtual machine. Kali Linux is preinstalled with over 600 penetration-testing programs, including nmap (a port scanner), Wireshark (a packet analyzer), John the Ripper (a password cracker), Aircrack-ng (a software suite for penetration-testing wireless LANs), Burp suite and OWASP ZAP (both web application security scanners).

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