RAT/HacDef is classified as a RAT.
RATs are software tools that allow the changing of system settings remotely.
The Fortinet Anti-Spyware Research Team is currently in the process of creating a detailed description for this Spyware.
For additional information about RAT, and how Fortinet classifies Spyware threats please see Fortinet's paper in PDF format:
Spyware Classification and Terms.