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Abstract

As large language models (LLMs) expose systemic security challenges in high risk applications, including privacy leaks, bias amplification, and malicious abuse, there is an urgent need for a dynamic risk assessment and collaborative defence framework that covers their entire life cycle. This paper focuses on the security problems of large language models (LLMs) in critical application scenarios, such as the possibility of disclosure of user data, the deliberate input of harmful instructions, or the models bias. To solve these problems, we describe the design of a system for dynamic risk assessment and a hierarchical defence system that allows different levels of protection to cooperate. This paper presents a risk assessment system capable of evaluating both static and dynamic indicators simultaneously. It uses entropy weighting to calculate essential data, such as the frequency of sensitive words, whether the API call is typical, the realtime risk entropy value is significant, and the degree of context deviation. The experimental results show that the system is capable of identifying concealed attacks, such as role escape, and can perform rapid risk evaluation. The paper uses a hybrid model called BERT-CRF (Bidirectional Encoder Representation from Transformers) at the input layer to identify and filter malicious commands. The model layer uses dynamic adversarial training and differential privacy noise injection technology together. The output layer also has a neural watermarking system that can track the source of the content. In practice, the quality of this method, especially important in terms of customer service in the financial industry. We find that it is much faster to handle new attacks, about three times faster than the previous solution. Most importantly, although the speed is faster, the quality of the text generated is still as good as before and unaffected. We experimented with NVIDIA A100 GPU clusters and real industry datasets, and it turned out that the framework worked. The analysis found that while the defence overhead of hyperscale models grew more slowly and not as fast as linear, they could do better in defending against multimodal attacks. The approach proposed in this paper provides a viable technical solution to LLM security governance, which can be used in multimodal learning and colearning in these other application scenarios.