# A Survey on Secure WiFi Sensing Technology: Attacks and Defenses
## 3 Attacks Against WiFi Sensing
### Discussion  
By reviewing the above-mentioned works on the attack techniques against WiFi sensing, some lessons have been learned from these efforts. **Cost and efficiency**: The cost and efficiency of executing attacks on WiFi sensing systems vary significantly between active and passive approaches, influencing their practicality and prevalence. For active attacks, additional specialized devices are often required to carry out the attack effectively. For example, RIStealth relies on a metasurface to manipulate wireless signals, while WiAdv employs a full-duplex device to interfere with the sensing process. Although these devices can achieve a high attack success rate (e.g., over 70% in both RIStealth and WiAdv), their high cost (e.g., over USD 1000 per device) makes such attacks economically impractical for most attackers. On the other hand, the use of commercial UAVs in attacks like Wi-Peep reduces the cost barrier, with devices priced at around USD 200, making them a more feasible option for attackers. In contrast, passive attacks are far more cost-efficient, as they typically require only a standard WiFi device to receive and analyze wireless signals. This significantly lowers the burden on attackers, both financially and logistically. Moreover, passive attacks often achieve high success rates. For instance, ActListener demonstrates an attack success rate of over 80%, showcasing the effectiveness of this approach. The disparity in cost and efficiency between active and passive attacks highlights a critical consideration for the design of secure WiFi sensing systems. While active attacks may pose a higher technical challenge, their high cost limits their widespread adoption. Passive attacks, on the other hand, are more accessible and equally, if not more, effective, making them a more immediate threat. **Existing attacks**: It is important to recognize that attacking the wireless channel is generally easier than directly compromising the Tx or Rx devices. This is primarily because the wireless channel serves as an open medium that can be accessed and monitored by anyone within range, making it vulnerable to a wide range of attacks such as signal interference, jamming, or eavesdropping. In contrast, the Tx and Rx devices are typically under the control of authorized users, often equipped with security protocols, authentication mechanisms, and physical access controls that make them much harder to breach. As a result, it is more feasible to exploit the inherent openness of the wireless channel rather than attempting to gain access to APs of the WiFi sensing system. **Advanced attacks**: Moreover, there are some advanced attack methods exploited in attacking wireless communication systems that may also be used for sensing information eavesdropping in the future. One may better defend against these attacks based on clear knowledge of them. (1) Man-in-the-middle (MITM) attacks [77]: In a MITM attack, the attacker secretly intercepts and potentially alters the communication between two parties without their knowledge. In the context of WiFi sensing, an MITM attacker could position themselves between the sensing device (e.g., a WiFi router) and the target (e.g., a user or object being sensed). By doing so, the attacker could intercept the sensing data, modify them to introduce errors, or even inject malicious data to mislead the sensing system. (2) Supply chain attacks [78]: Supply chain attacks target the hardware, software, or services that are part of the WiFi sensing ecosystem. In such attacks, the attacker compromises a component of the supply chain (e.g., a WiFi chip manufacturer, a firmware provider, or a third-party software library) to introduce vulnerabilities or malicious code into the sensing system. For instance, an attacker could tamper with the firmware of a WiFi router to secretly collect and transmit sensing data to an external server. (3) Proactive eavesdropping: Proactive eavesdropping is increasingly employed to steal communication content [79].