Model-based Evaluation: from Dependability Theory to Security

How to quantify security is a classic question in the security community that until today has had no plausible answer. Unfortunately, current security evaluation models are often either quantitative but too specific (i.e., applicability is limited), or comprehensive (i.e., system-level) but qualitative. The importance of quantifying security cannot be overstated, but doing so is difficult and complex, for many reason: the “physics” of the amount of security is ambiguous; the operational state is defined by two confronting parties; protecting and breaking systems is a cross-disciplinary mechanism; security is achieved by comparable security strength and breakable by the weakest link; and the human factor is unavoidable, among others. Thus, security engineers face great challenges in defending the principles of information security and privacy. This thesis addresses model-based system-level security quantification and argues that properly addressing the quantification problem of security first requires a paradigm shift in security modeling, addressing the problem at the abstraction level of what defines a computing system and failure model, before any system-level analysis can be established. Consequently, we present a candidate computing systems abstraction and failure model, then propose two failure-centric model-based quantification approaches, each including a bounding system model, performance measures, and evaluation techniques. The first approach addresses the problem considering the set of controls. To bound and build the logical network of a security system, we extend our original work on the Information Security Maturity Model (ISMM) with Reliability Block Diagrams (RBDs), state vectors, and structure functions from reliability engineering. We then present two different groups of evaluation methods. The first mainly addresses binary systems, by extending minimal path sets, minimal cut sets, and reliability analysis based on both random events and random variables. The second group addresses multi-state security systems with multiple performance measures, by extending Multi-state Systems (MSSs) representation and the Universal Generating Function (UGF) method. The second approach addresses the quantification problem when the two sets of a computing system, i.e., assets and controls, are considered. We adopt a graph-theoretic approach using Bayesian Networks (BNs) to build an asset-control graph as the candidate bounding system model, then demonstrate its application in a novel risk assessment method with various diagnosis and prediction inferences. This work, however, is multidisciplinary, involving foundations from many fields, including security engineering; maturity models; dependability theory, particularly reliability engineering; graph theory, particularly BNs; and probability and stochastic models

Towards evaluating security implementations using the Information Security Maturity Model (ISMM)

Information security is a common and ever-present concern for both private and public sector organizations. Information security protects information from a wide range of threats, risks, and vulnerabilities in order to ensure information availability, integrity and confidentiality, and hence business continuity. This research seeks to use a heuristic-based investigation of the Information Security Maturity Model (ISMM), developed by the author, combined with a thorough review of existing models, to suggest considerable extensions. This shall merit various applications leading to establish a connective body of knowledge and bridge a gap in existing literature and industry regarding the information security implementation in light of use of international standards and models. The ISMM model is neither based on a specific technology/protocol (e.g. PKI, IPSec, SSL) nor a certain system/product (e.g. Firewall, Antivirus, IDS), but rather an engineering approach towards a structured and efficient implementation of those technologies. The ISMM is a security-centric model that consists of five distinctive and ordered security layers, each of which has its own definition, scope, and characteristics. The model reflects the three key security processes (prevention, detection and recovery) and captures effects of people (visibility and sophistication) on every layer. It aims essentially to assess the maturity of any security implementation of any size and type (i.e. device, system, or environment). New extensions of the ISMM work are put forward. Literature review is augmented by introducing a new classification of information security models. Additionally, new abstractions are introduced, first: the abstraction of security conceptual boundaries, which signifies rational priorities and captures the unavoidable interferences between information and physical security in any security context, second: the abstraction of ratios of resources utilization (i.e. computational power, energy, memory, and other costs). Further extensions include a new attack model that classifies attacks in terms of their impact. This leads to a new approach for analyzing attacks and study adversary’s capabilities at different layers of both the ISMM and network models in the whole system, as one integrated entity against both single and hybrid attacks. As an example of one possible mapping and compatibility of the ISMM with other security-related models, the ISMM layers are mapped to their pertinent peers in network models (i.e. ISO/OSI and TCP/IP), which offers more information about security controls at each layer and its contribution to the actual overall security posture. The ISMM offers a prompt and structured approach to identify the current security state of small communication devices, computing platforms, and large computing environments in a consistent manner. A cost-effective realization is achieved through the optimization of IT and security expenditure. Therefore, the model assists to minimize deficiencies in security implementation. Also, the identification of needs and goals of the following level in the ISMM hierarchy allows a strategic approach proportional to allowable resources to take place, as a result, both goals are reached and cost is reduced much faster. This work is believed to facilitate grounds for future research endeavors such as applying these propositions on simulated examples, real life case studies, and developing a formula for the optimized distribution of security resources in a consistent manner with the best possible security level