About qbittorrent : qbittorrent is a torrent client, an alternative to utorrent . It's a GUI based cross platform free software based on Qt toolkit. We know that Kali Linux's base package is constructed in Debian, so we need to add http://http.packages.debian.org to sources.list file. To do this, 1. open any text editor and edit sources.list file, located in /etc/apt directory, with an entry deb http://http.packages.debian.org import deb packages . 2. type apt-get install qbittorrent on the root terminal window and press enter 3. Once qbittorrent is installed, type qbittorrent on the root terminal window and press enter and, you are set to go.