# A Survey on Secure WiFi Sensing Technology: Attacks and Defenses
## 1 Introduction
Even though existing works have attempted to overcome these challenges by designing novel sensing techniques, these works are still removed from ubiquitous and practical deployment. Thus, it is important to figure out the challenges they face and the limitations that have not been addressed. Moreover, the development trends should be pointed out to illuminate the potential directions of secure WiFi sensing. Therefore, there is a strong need for a comprehensive study of secure WiFi sensing. To this end, we conducted a systematic survey of secure WiFi sensing technology, including both the methods to attack WiFi sensing systems and the methods to defend against the corresponding attacks. As for the attack methods, in most cases, attackers either actively tamper with the sensing results or passively eavesdrop on the sensing data, so we categorized the existing attack methods into active attack and passive attack. As for the defense methods, in most cases, users either actively adopt defense strategies themselves or are passively secured by a third party, so we also categorized the existing defense methods into active defense and passive defense. Research works in each category were well discussed and compared, respectively. There have been some related surveys that provide a summary of particular scopes, such as secure wireless communication, IoT security, and WiFi sensing. We compared and herein summarize them in detail, finding that none of the current surveys focus on summarizing the existing technologies for attack on and defense of WiFi sensing and analyzing their key challenges. As we mentioned, a comprehensive survey is necessary and important for researchers and application developers. This survey is expected to inspire researchers and developers to conduct further research in secure WiFi sensing and build various applications to realize privacy-preserving, reliable, ubiquitous, and accurate WiFi sensing in real life. The main contributions of this paper are summarized as follows:  
* **Complete picture and novel taxonomy:** We present a complete picture of the literature in the area of secure WiFi sensing and propose a novel taxonomy for technologies for attack and defense of WiFi sensing, respectively, which guides the first step;
* **Inclusive and up-to-date coverage:** Our survey is inclusive, encompassing the latest advancements in secure WiFi sensing technologies. By integrating recent developments, we ensure that our work remains relevant and valuable to the research community;
* **Comprehensive comparison and summary:** We comprehensively compare and summarize existing technologies for attack and defense of WiFi sensing to provide readers with a thorough understanding of this area;
* **Identification of key challenges and future directions:** Our survey discusses the key challenges and future directions, which may inspire researchers and developers to carry on further research in WiFi sensing and build various applications to realize privacy-preserving, reliable, ubiquitous, and accurate WiFi sensing. As shown in Figure 1, the structure of this survey is organized as follows. Section 2 introduces the scope and taxonomy of this survey. Sections 3 and 4, respectively, summarize and discuss the research works of attacks against and defenses on existing WiFi sensing systems. Based on the analysis and summary of these works, Section 5 discusses potential challenges and opportunities on the topic of secure WiFi sensing. Finally, we conclude this survey in Section 6.