The management of technical debt related to non-functional properties such as security, reliability or other trustworthiness dimensions is of paramount importance for critical systems (e.g., safety-critical, systems with strong privacy constraints etc.). Unfortunately, diverse factors such as time pressure, resource limitations, organizational aspects, lack of skills, or the fast pace at which new risks appears, can result in an inferior level of trustworthiness than the desired or required one. In addition, there is increased interest in considering trustworthiness characteristics, not in isolation, but in an aggregated fashion, as well as using this knowledge for risk quantification. In this work, we propose a trustworthiness debt measurement approach using 1) established categories and subcategories of trustworthiness characteristics from SQuaRE, 2) a weighting approach for the characteristics based on an AHP method, 3) a composed indicator based on a Fuzzy method, and 4) a risk management and analysis support based on Monte Carlo simulations. Given the preliminary nature of this work, while we propose the general approach for all trustworthiness dimensions, we elaborate more on security and reliability. This initial proposal aims providing a practical approach to manage trustworthiness debt suitable for any life cycle phase and bringing the attention to aggregation methods.

Industries from very diverse domains are realising that security should not be treated in a reactive way (e.g., once the cyberattack has happened). This way, security-related requirements and risks need to be continuously managed, and the need of integrating technical measures should be continuously assessed. In some cases, some decisions led, intentionally or unintentionally, to debt related to security aspects. This security debt is thus incurred when limited approaches or solutions are applied to reach the expected security levels of the system in operation. Identifying and making explicit security debt items is a challenge for companies. In this work, we analyse the literature on security debt to provide initial insights on the topic. Concretely, we discuss its definition, identify its most salient characteristics, present approaches for integrating its management in the product life-cycle, and to present categories and examples of security debt items.