Information is an important business asset in today’s enterprises. Hence enterprise information security is an important system quality that must be carefully managed. Although enterprise information security is acknowledged as one of the most central areas for enterprise IT management, the topic still lacks adequate support for decision making on top-management level.

This composite thesis consists of four articles which presents the Enterprise Information Security Assessment Method (EISAM), a comprehensive method for assessing the current state of the enterprise information security. The method is useful in helping guide top-management’s decision-making because of the following reasons: 1) it is easy to understand, 2) it is prescriptive, 3) it is credible, and 4) it is efficient.

The assessment result is easy to understand because it presents a quantitative estimate. The result can be presented as an aggregated single value, abstracting the details of the assessment. The result is easy to grasp and enables comparisons both within the organization and in terms of industry in general.

The method is prescriptive since it delivers concrete and traceable measurements. This helps guide top-level management in their decisions regarding enterprise-wide information security by highlighting the areas where improvements efforts are essential.

It is credible for two reasons. Firstly, the method presents an explicit and transparent definition of enterprise information security. Secondly, the method in itself includes an indication of assessment uncertainty, expressed in terms of confidence levels.

The method is efficient because it focuses on important enterprise information security aspects, and because it takes into account how difficult it is to find security related evidence. Being resource sparse it enables assessments to take place regularly, which gives valuable knowledge for long-term decision-making.

The usefulness of the presented method, along with its development, has been verified through empirical studies at a leading electric power company in Europe and through statistical surveys carried out among information security experts in Sweden.

The success from this research should encourage further researcher in using these analysis techniques to guide decisions on other enterprise architecture attributes.