Security terminology. Security is concerned with protecting systems against malicious attacks that seek to compromise the confidentiality, integrity or availability of the system. Historically, the security community has been distinct from the dependability community and has developed its own terminology, but the most recent version of the dependability taxonomy attempted to document a minimum consensus on the concepts of dependable and secure computing in order to facilitate more technical interaction between the two communities. In particular, security can be considered to be a form of dependability that focuses on the attributes of confidentiality, integrity and availability in the presence of malicious faults. However, security terminology uses a variety of terms such as attack, vulnerability and intrusion to describe security- related faults, failures and errors. An intrusion is a malicious interaction fault that compromises the security of a system [31]. This is not the same as an attack because a system can be attacked unsuccessfully. If the system can withstand attack, intrusions can be prevented. In other words, an attack is an intrusion attempt, and an intrusion is the result of a successful attack. In fact, every intrusion has two underlying causes:
Security terminology. Security can be defined as a system property that allows the system “to perform its mis- sion or critical functions despite risks posed by threats” (Xxxxxx, 2013), where a threat is de- fined as “the potential source of an adverse event” (Xxxxxx, 2013). In every system there is a set of assets, i.e., values that need to be protected against a mali- cious adversary. A vulnerability is described as a flaw in the system that enables a threat target- ing one of the system assets. An attack is real- ization of a threat by exploiting a vulnerability in an attempt to break a system asset as it is demonstrated in Figure 1. Countermeasures are “actions, devices, procedures, or techniques that meet or oppose (i.e., counters) a threat, a vulner- ability, or an attack by eliminating or preventing it” (Xxxxxx, 2013). One can classify them as (i) preventive, e.g., encryption, (ii) detective, e.g., intrusion detection systems, (iii) responsive, e.g., blacklisting of a detected attack source (Xxxxx et al., 2010). Countermeasures support security objectives, e.g., confidentiality and authentica- tion. Security process is a continuous process and it can be split into following steps (Kizza, 2017): (i) system security policy formulation, (ii) a secu- rity requirements elicitation, (iii) a threat iden- tification, (iv) a threat analysis, (v) a vulnera- bility identification and assessment, (vi) a secu- rity certification, (vii) a security monitoring and auditing. A security policy can be defined as a set of policies and procedures that regulates ac- tions of people and systems within the informa- tion system security domain (Xxxxx et al., 2017). A policy can be evaluated for violations and en- forced by mechanisms, it states how a high level security goal is achieved. Applied to a system level, two main groups of policies can be identi- fied (XxXxxxxx, 2005): (i) provisioning policies that prescribe a configuration meeting system re- quirements; (ii) authorization policies that map entities and resources into allowable actions. The latter is split into authentication policies respon- sible for stating how an identity of an entity can be established, and access control policies map- ping the established identity to a set of corre- sponding rights.
