# Resilience in the Cyberworld: Definitions, Features and Models
## 3 Key Actions and Attributes  
Section 2 introduced the key actions anticipation, resistance, recovery, detecting and adaptation. These five key actions can be defined as follows. Comparable definitions are listed in [6; 8; 9; 33], for example:  
* **Anticipation:** Anticipation is a process that enables the system to prepare for a disruption or an attack that may occur. * **Resistance:** Resistance is the ability to withstand the effects of a disruption or an attack and maintain a certain level of functionality. * **Recovery:** The system must be able to recover the lost functionality. * **Adaptation:** The system must be able to put itself in a state by responding more efficiently to the disturbance in the future. This essentially means that the system will lose less functionality in the future and the recovery time will also be less. * **Detection:** Detection means that a system can detect a disturbance or an attack in order to initiate appropriate countermeasures. \begin{table}
\begin{tabular}{c c c} \hline \hline
**No.** & **Publication** & **Key action** \\ \hline
**1** & [PERSON], 1976 & \\
**2** & [PERSON], 2007 & \\
**3** & [PERSON], 2008 & \\
**4** & [PERSON], 2011 & \\
**5** & [PERSON], 2013 & \\
**6** & [PERSON], 2015 & \\
**7** & [PERSON], 2016 & \\
**8** & NIST, 2018 & \\
**9** & [PERSON], 2020 & \\
**10** & [PERSON], 2020 & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Sources mentioning key actions. Each key action comprises several attributes (In the publications presented here, the terms attribute, feature and measure were used synonymously. For the sake of clarity, only the term attribute will be used in this article, representing Feature and Measure). These attributes can be derived directly from the definitions or were explicitly mentioned in the publications. The attached descriptions of the attributes can be found in this way in [11; 47], for example:  
* **Robustness:** Still function reliably under adverse conditions. * **Reliability:** Continuity of service. * **Availability:** Readiness for usage. * **Evolvability:** Ability to accommodate changes. * **Adaptability:** Ability to anticipate to changes. * **Security:** Crime Prevention. * **Safety:** Accident prevention. * **Assessability:** Check for correctness of data (plausibility check). * **Integrity:** Nonoccurrence of incorrect system alterations. Ref. [2] describes the four main attributes of a resilient service. First, a resilient service must be able to detect and correct errors. Further, the resilient service must be so robust and reliable that a user expects the service not to fail. If the service is capable of always detecting \(n\) errors and recovering from those errors, the \(n+1\) error is not catastrophic. This only applies under the condition that the system offers perfect detection and recovery of \(n\) errors. The resilient service is therefore able to anticipate the \((n+1)th\) error in such a way that its negative consequences for the service can be minimized. This corresponds to a simple definition of evolvability. As a fourth key attribute, [PERSON] [2] cites the ability of a resilient service to tolerate abuse by a single user in such a way that this abuse has negligible impact on the other users of the service. [PERSON] does not specify misuse, but if a malicious and intentional action is assumed, then this misuse protection corresponds to the security feature of availability. [PERSON] summarizes the following features: robustness, reliability, evolvability and security. Ref. [11] claims that robustness under all conditions is the most important property of a resilient system. According to [PERSON] [11], this robustness is directly related to the reliability of a resilient system. This connection is obvious, since a system that is not stable cannot be reliable either. This understanding of robustness and reliability is also illustrated in [13]. Assessability is also an important property, because a resilient system must be able to validate the correctness or plausibility of sensor data, for example.