Dempster-Shafer theory, or evidence theory, is a mathematical framework for describing the state of a system based on incomplete and imperfect knowledge. Its use in the propagation of beliefs and the combination of information becomes relevant in the presence of imprecise and uncertain data. By introducing the notion of information vulnerability, we focus on the case where an external agent intelligently corrupts a minority of sources. We consider the conflict thus generated as a valuable quantity for corruption detection. Several attack models are studied during numerical simulations in a knowledge management system. We analyse the robustness of the knowledge management system as a function of the discretion of the corrupting agent. The usual rule for combining information is compared with a new rule for fine-grained conflict management.