In this paper we discuss the core capabilities that a system needs to provide in order to ensure resilience. In short such a system needs to be capable of detecting its own state in the sense of recognizing errors and then reacting appropriate in order to restore its full functionality. In addition we argue why security is the essential prerequisite to achieve resilience. If a system can be compromised the attacker is in control of what the system does i.e. he can for example switch it off or simply disable error recovery mechanisms. This is the reason why we argue for proper design and assessment of security means used in any system that aims at achieving resilience.