[Ruler](https://attack.mitre.org/software/S0358) is a tool to abuse Microsoft Exchange services. It is publicly available on GitHub and the tool is executed via the command line. The creators of [Ruler](https://attack.mitre.org/software/S0358) have also released a defensive tool, NotRuler, to detect its usage.(Citation: SensePost Ruler GitHub)(Citation: SensePost NotRuler)