Abstract
This paper presents an open-source tool to support the quantitative assessment of software reliability and cyber security. The tool enables assessment of a system’s security from penetration-testing data and can be used to estimate the number of vulnerabilities remaining. This approach will enable organisations that acquire software to establish quantitative requirements for inclusion in contracts, thereby providing clear requirements for software and system developers to meet. The tool will enable contractors to regularly assess the security of their software, which will facilitate the identification and reporting of programs that may fail to achieve contractually specified security objectives.