All modern computer users need to be concerned about information system security (individuals and organisations). Many businesses established various security structures to protect information system security from harmful occurrences by implementing security procedures, processes, policies, and information system security organisational structures to ensure data security. Despite all the precautions, information security remains a disaster in Tanzania's learning institutions. The fundamental issue appears to be a lack of awareness of crucial information security factors. Various companies have different security issues due to differences in ICT infrastructure, implementations, and usage. The study focuses on identifying information system security threats and vulnerabilities in public higher learning institutions in Tanzania, particularly the Institute of Accountancy Arusha (IAA). The study involved all employees of IAA, academics, and other supporting staff, which totalled 302, and the sample size was 170. The study utilised a descriptive research design, where the quantitative methodology was used through a five-point Likert scale questionnaire, and found that key factors that affect the security of information systems at IAA include human factors, policy-related issues, work environment and demographic factors. The study proposed regular awareness and training programs; an increase in women's awareness of information system security; proper policy creation and reviews every 4 years; promote actions that lessen information system security threats and vulnerabilities, and the creation of information system security policy documents independently from ICT policy.