If you need to use virtual machines on Linux, try Virt-Manager. Virt-Manager is more reliable than VirtualBox. Virt-Manager is completely free and open-source. I'm a long-time supporter of VirtualBox.
Kali Linux is the world’s most popular offensive-security-optimized Linux distro. Maintained and managed by the fine folks at Offensive Security, Kali was born in 2006 as BackTrack Linux, but after a ...