LLM based question answering systems have been used in healthcare, education,and customer support, and in these settings user prompts often contain names, health conditions, contact details, or other sensitive clues, which makes privacy protection at inferencetime hard to avoid, especially when the service is deployed as a black box. Many existingdefenses still rely on retraining or relatively rigid filtering rules, so they do not adapt wellwhen contextual sensitivity changes from one interaction to another. This paper proposes aprivacy protection framework for LLM QA at the question answer pair level. The frameworkestimates exposure risk with a probabilistic graphical model, then adjusts mitigation strengththrough threshold based control. In the protection stage, sanitization, abstraction, and calibrated noise are used together, so stronger intervention can be applied to more sensitive inputswhile ordinary interactions are affected less. Experiments on a SafetyBench derived datasetshow that the framework can reduce privacy risk and still keep answer utility at a useful level,with relatively low computational overhead.
Research Article
Open Access