A great tool that we often add to Kali is htop. Htop is a command-line tool similar to Windows Task Manager. It is important to know the rate of use for memory, swap-file, CPU, cycles and IOPS. Htop lets you use the mouse to sort by any category, and can mean an improvement in scan performance. This is the same information that the Top tool gives you, but being an ncurses application, it gives you a more modern GUI-like feel without using large quantities of resources to show the resource data. For the following image, we started a long scan nmap -A 100.0.0.0/8. The Iceweasel lines are the Debian/Kali all-free-software version of Firefox, which has the same memory-hogging behavior of Firefox. Nmap scans use a lot of CPU cycles, and not so much memory: