# A Survey on Secure WiFi Sensing Technology: Attacks and Defenses
## 4 Defenses for WiFi Sensing
### Discussion  
By reviewing the above-mentioned works on the defense techniques for WiFi sensing, some lessons can be learned from these efforts.  
**Cost and efficiency**: For active defense, users have several options to enhance the security of their WiFi sensing systems, including employing additional devices or modifying the WiFi hardware or firmware. For instance, IRShield leverages a metasurface to reduce the detection rate of attackers to less than 5%. However, this approach comes with a significant cost, as dedicated metasurfaces can exceed USD 1000, making it a less feasible option for many users. Another example is WiCloak, which modifies the WiFi hardware to increase the localization error by 22 times compared to standard WiFi systems. While this method is effective, it requires technical expertise to implement, which may be beyond the capabilities of typical users. For normal users without specialized knowledge, purchasing an additional device is often the most practical choice. However, the high cost of such devices can be a deterrent. In this case, turning to a third-party solution for protection at a moderate cost may be a more viable alternative, in other words, choosing passive defense. Third-party solutions can provide advanced security features without requiring users to modify their hardware or firmware directly. This approach not only reduces the burden on users but also ensures that the system remains secure against evolving threats.  
**Sensing target**: Existing defense techniques are designed to protect the wireless channel from unauthorized access, ensuring that sensitive data are shielded from potential attackers. However, some of these strategies focus on obfuscating the wireless channel entirely to prevent attackers from extracting useful information. While this approach successfully blocks adversaries from accessing the channel, it presents a significant drawback: legitimate users are also unable to perform sensing operations or provide related services. This compromise essentially limits the core functionality of the system, raising concerns about its practical deployment, especially in environments where continuous and reliable sensing is critical. Moreover, several defense mechanisms propose altering the hardware or software of commercial devices or modifying the format of WiFi packets to enhance security. While these techniques may offer robust protection in theory, they come with notable limitations in real-world applications. The requirement to modify commercial off-the-shelf devices is often impractical, as most users and organizations lack the resources, technical expertise, or willingness to implement such changes. Additionally, altering standard protocols or packet structures can introduce compatibility issues, making it difficult to integrate these defenses into existing networks. These constraints significantly hinder the availability and scalability of these methods, limiting their usefulness in large-scale or widely distributed systems where uniform adoption is challenging.  
**Third parties**: While some efforts have been made to secure WiFi sensing through the involvement of external entities, this introduces additional concerns regarding the trustworthiness and security of these third parties. Relying on external organizations or service providers to manage or secure sensing operations raises the question of whether these parties can be fully trusted to handle sensitive data responsibly and without introducing new vulnerabilities. The involvement of third parties inevitably expands the attack surface, as it creates more points of potential failure or compromise. If these external entities are not properly vetted or secured, they themselves could become targets for attackers, ultimately undermining the very security they are meant to uphold. To mitigate these risks, cryptographic algorithms can be employed to enhance the security of WiFi sensing when third parties are involved.