The relevance of this article is determined by the fact that modern large cities can increasingly be viewed as relatively stable administrative-territorial units and increasingly act as complex socio-technological systems operating in a state of constant uncertainty. This problem is particularly acute in large Russian cities in Northern Eurasia, where harsh climatic conditions, dependence on centralized heating, extensive infrastructure, digitalization of governance, and heterogeneity of the urban population increase the likelihood of cascading failures. The scientific problem of the study lies in the insufficient development of an integrated concept of urban socio-technological security. Existing approaches often analyze social, technical, informational, and managerial risks separately, whereas in the real urban environment they form a unified system of mutual reinforcement. The methodological basis of the article is the interdisciplinary framework of the sociology of instability, combining ideas from the sociology of risk, the theory of reflexive modernity, systems analysis, urban studies, and security studies. This paper utilizes a conceptual analysis of the categories of “social instability”, “social turbulence”, “social chaos”, “social risks”, “danger”, and “threat”, as well as elements of systemic and institutional approaches. The research's scientific results, firstly, clarify the distinction between socio-technological danger and socio-technological threat. Danger is understood as the potential for a social actor to fail to achieve its intended results due to the unprofessional application of social technologies or the inability to adequately interpret the actions of other actors. Threat, in contrast, implies a targeted destructive impact carried out by a specific actor using organizational, information, digital, or manipulative technologies. Secondly, it is shown that the key vulnerability of a large city is associated with the gap between the high interdependence of infrastructures and the fragmentation of institutional governance. Thirdly, it was revealed that the expert community considers the public's and institutions' understanding of socio-technological hazards to be inadequate. This emphasises the need for systemic education, specialist training and the development of a safety culture. The findings substantiate the need to create an urban socio-technological security system as a multi-layered institutional framework, including a regulatory framework, technical protection, digital monitoring, dispatching systems, risk communication, educational programs, a framework for countering disinformation, independent expertise, and public participation mechanisms. Such a system should be focused not only on eliminating the consequences of crises but also on the early detection of pre-crisis signs, maintaining reliable feedback, and enhancing the urban community's capacity for rational, collaborative action in unstable conditions.