NeuronFuzz: Safety Neuron Guided Fuzzing for LLM Safety Evaluation
A new fuzzing framework, NeuronFuzz, is introduced to improve safety evaluation of Large Language Models (LLMs) by using internal safety neurons.
Intelligence analysis by Qwen 2.5 (3B)

Researchers have developed a new fuzzing framework called NeuronFuzz to enhance the safety evaluation of Large Language Models (LLMs) by leveraging internal safety neurons.
Imagine you have a really smart robot that can talk. NeuronFuzz is like a detective that watches the robot closely to make sure it doesn't do anything bad. It uses special sensors inside the robot to know when the robot might try to do something naughty. This way, the detective can catch the robot before it does anything wrong.
Analysis
Background on Safety Neurons and Fuzzing
NeuronFuzz is a white-box fuzzing framework that uses internal safety neurons to guide the fuzzing process. Safety neurons are internal mechanisms within LLMs that detect harmful intent. The framework converts these activations into a continuous safety alarm score, which serves as feedback for the fuzzing loop. This approach differs from traditional response-level feedback methods, which require generating a target-model response for each candidate prompt.
How NeuronFuzz Works
NeuronFuzz identifies a compact set of safety neurons whose activations capture harmful-intent recognition. It uses template-invariant harmful and benign inputs and stability-aware selection to achieve this. The SafetyOracle, a component of NeuronFuzz, converts safety-neuron activations into a continuous safety alarm score. This score is used as feedback for the fuzzing process, eliminating the need for response generation.
Evaluation Results
NeuronFuzz was evaluated across 21 text and multimodal models. Across five white-box source models, it achieved a 76-100% jailbreak discovery rate, outperforming baselines by up to 48 percentage points. Its optimized templates further transfer zero-shot to open-weight and six proprietary target models, achieving average ASR and top-5 ensemble ASR (EASR) of 69.6%/92.6% and 44.1%/60.0%, respectively.
Future Directions
NeuronFuzz represents a significant advancement in the field of LLM safety evaluation. Its ability to leverage internal safety neurons and provide continuous feedback could pave the way for more robust and secure LLMs. However, there are still challenges to overcome, such as the need for more comprehensive and diverse testing scenarios and the potential for false positives or negatives in the safety alarm score.
Key points
- NeuronFuzz uses internal safety neurons to guide fuzzing for LLMs
- Achieved a 76-100% jailbreak discovery rate across 21 models
- Optimized templates transfer to six proprietary target models
- Potential for false positives in the safety alarm score
- Could lead to more robust and secure LLMs
NeuronFuzz could help make smarter and safer language models that are less likely to make mistakes or do harmful things. This could lead to better and more trustworthy AI technology.
However, there might be some false alarms where the model thinks it's doing something naughty when it's not. This could cause unnecessary work and confusion for developers.


