Fault attacks consist in changing the program behavior by injecting faults at run-time in order to break some expected security properties. Applications are hardened against fault attack by adding countermeasures. According to the state of the art, applications must now be protected against multifault injection [23], [33]. As a consequence developing applications which are robust becomes a very challenging task, in particular because countermeasures can be also the target of attacks [4], [20]. The aim of this paper is to propose an assisted methodology for developers allowing to harden an application against multifault attacks, addressing several aspects: how to identify which parts of the code should be protected and how to choose and place the appropriate countermeasures, giving guarantees on the robustness of the protected program.