Standalone virtual reality (VR) headsets process highly sensitive personal, professional, and health-related data, yet their susceptibility to non-contact physical side channels remains largely unexplored. Existing side-channel attacks typically require malicious software execution or physical access to peripherals, making them conspicuous and potentially patchable. This paper introduces ThermalTap, the first passive, non-contact side-channel attack that fingerprints VR applications solely from the long-wave infrared (LWIR) radiation emitted by the headset chassis. By treating a headset's thermal signature as a high-fidelity proxy for internal computational workloads, ThermalTap enables remote application inference at meter-scale distances without any device interaction. To achieve robust performance in real-world settings, the system combines a commodity thermal camera with a multi-modal sensor suite (capturing ambient temperature, humidity, and airflow) to normalize environmental noise. We evaluate ThermalTap using six applications across three commercial standalone headsets. In indoor settings, ThermalTap identifies applications with over 90% accuracy using only 10 seconds of thermal camera data. Under outdoor conditions, with longer session-level observations, several applications remain identifiable despite environmental variability, with the strongest outdoor application reaching 81% accuracy. Our findings establish thermal radiation as a fundamental and unavoidable privacy risk for immersive systems, exposing a critical security gap that bypasses current software-level protections and physical access controls.

翻译：独立虚拟现实（VR）头显处理高度敏感的个人、职业及健康相关数据，但其对非接触式物理侧通道的易感性仍鲜有探究。现有侧通道攻击通常需要恶意软件执行或物理接触外设，使其易于被察觉且存在修补可能。本文提出ThermalTap，这是首个通过头显机箱发射的长波红外（LWIR）辐射被动、非接触式指纹识别VR应用的侧通道攻击。通过将头显的热特征视为内部计算工作负载的高保真代理，ThermalTap能够在米级距离实现无需设备交互的远程应用推断。为在真实场景中实现稳健性能，该系统将商用热成像相机与多模态传感器套件（捕获环境温度、湿度与气流）相结合，以归一化环境噪声。我们使用六款应用对三款商用独立头显进行了评估。在室内环境中，ThermalTap仅需10秒热成像数据即可实现超过90%的应用识别准确率。在户外条件下，通过更长时间的会话级观测，尽管存在环境变异性，多款应用仍可被识别，其中最强户外应用的准确率达到81%。我们的研究证实热辐射是沉浸式系统固有的不可规避隐私风险，揭示出当前软件级防护与物理访问控制均无法解决的关键安全缺口。