CCleaner (/ ˈ s iː k l iː n ər /, originally Crap Cleaner), developed by Piriform (a company acquired by Avast in 2017), is a utility used to clean potentially unwanted files and invalid Windows Registry entries from a computer. It combines several cracking modes in one program and is fully configurable for your particular needs (you can even define a custom cracking mode using the built-in compiler supporting a subset of C). John the Ripper is designed to be both feature-rich and fast.