LLM-WFIN: A Fine-Grained Large Language Model (LLM)-Oriented Website Fingerprinting Attack via Fusing Interrupt Trace and Network Traffic

Popular Large Language Models (LLMs) access uses website browsing and also faces website fingerprinting attacks. Website fingerprinting attacks have increasingly threatened website users to the leakage of browsing privacy. In addition to the often-used network traffic analysis, interrupt tracing exploits the microarchitectural side channels to be a new compromising method and assists website fingerprinting attacks on non-LLM websites with up to 96.6% classification accuracy. More importantly, our observations show that LLM website access performs inherent defense and decreases the attack classification accuracy to 6.5%. This resistance highlights the need to develop new website fingerprinting attacks for LLM websites. Therefore, we propose a fine-grained LLM-oriented website fingerprinting attack via fusing interrupt trace and network traffic (LLM-WFIN) to identify the browsing website and the content type accurately. A prior-fusion-based one-stage classifier and post-fusion-based two-stage classifier are trained to enhance website fingerprinting attacks. The comprehensive results and ablation study on 25 popular LLM websites and varying machine learning methods demonstrate that LLM-WFIN using post-fusion achieves 97.2% attack classification accuracy with no defense and outperforms prior-fusion with 81.6% attack classification accuracy with effective defenses.