# Vulnerability Assessment of Sensor Systems
## 5 Discussion of Validation Results
### General Remarks and Conclusions  
SVAM is defined as a sequentially ordered set of elementary processes. It can be considered a sequence of activities, but in reality, the work is iterative and more complicated because the evaluators often have to go back to the previously considered activities. This is typical for the CEM methodology. The elementary evaluation processes need even deeper structuring allowing one to distinguish details related to the particular AVA_VAN components (activities and data). The EEPs should be refined separately for each component and have implemented work units specific for the EAL (which can be applied when the supporting tool is being developed). The verification of the defined elementary evaluation processes (EEP) versus the contents of the work units defined in CEM was performed previously [51]. The knowledge bases should be ready to acquire knowledge details related to the most rigorous AVA_VAN.4 component. For lower assurance components, certain data properties representing knowledge may not be used or may be formulated less precisely than the high rigor requirements of AVA_VAN.4. This approach may facilitate knowledge reusability from one project to another. When knowledge exists related to the low EAL, it can be reused and supplemented for a higher EAL project. When ITSEF has high EAL knowledge at its disposal, it can also be reused after generalizing the relevant elements. The _InfoSourceTaxonomy_, _PotentialVulnerability_PV_, _AttackScenario_AS_, and _PenetrationTest_PT_ knowledge bases can be the foundation to work out the ITSEF knowledge assets. They have high potential for knowledge reusability and can be maintained in for future evaluation projects. _CEMattackTaxonomy_ can be helpful in the organization of these bases. _CCtaxonomy_ has auxiliary meaning and can be used to map the evaluated product to the general taxonomy, and to compare the product with others to find necessary information. The _VulRelatlssue_VRI_, _AreaOfConcern_AOC_, _ApplicableVulnerability_AV_, and the _PenetrationTest_PT_ bases are project-oriented and their reusability is limited. Currently, a simplified knowledge model is applied. The main concepts are represented by ontology classes. Individuals of these classes have:  
* data properties representing knowledge,
* object properties to model relationships between parts of knowledge. Considering the progress in the development of internet information services, especially data feeds, there is a possibility of deeper knowledge structuring. The planned software tool to support evaluators should be able to acquire external knowledge semiautomatically, but under human or machine learning control. ETR is a holistic report summarizing the evaluation results of all evidences for the claimed EAL, including the considered AVA_VAN. The CCMODE toolset [7; 59] is only designed to support the CC-related development process, but it has potential to be spread to the whole CC methodology as well. The author proposes extending the solutions of the CCMODE project, especially:  
* the simplified CEM implementation called \"self-assessment\",
* the concept of patterns of evaluation evidences. The \"self-assessment\" facility can be extended to full CEM implementation and the set of design patterns can be supplemented by the ETR pattern summarizing all evaluation efforts. The evaluator will be able to generate the ETR report semiautomatically with the use of the tool and on the basis of the ETR pattern and the knowledge acquired during the evaluation. The author's previous papers focusing on IT security evaluation are closely related to the SVAM presented here. A previous paper [53] introduced the general ontological CEM model. This \"high-level model\" can be used to integrate (within the planned tool) all CEM evaluation processes corresponding to the particular security assurance components embraced by the given EAL. One of the most important processes is the vulnerability assessment process (AVA_VAN) discussed in the paper.