Your Walls Are No Longer Walls
A piece of open-source software can map your body through them using only WiFi signals. No law stops it.
Last week, a security researcher on X who goes by @DoingFedTime was asked whether a Yagi antenna would stop the through-wall WiFi sensing software that had just gone viral on GitHub. His answer: “Not having wifi does.” When pressed, he added: “The attacker brings the router. You just have to be inside the signal path.”
Those two sentences are not about antennas. They are about whether the law has anything meaningful to say when someone can reconstruct a person’s body position, breathing rate, and heart rate from the other side of a wall, using hardware that costs $30, leaves no physical trace, and captures no image that any existing statute was written to address.
The answer, examined against the current state of federal law and constitutional doctrine, is almost nothing.
What WiFi DensePose Actually Does
In December 2022, researchers Jiaqi Geng, Dong Huang, and Fernando De la Torre at Carnegie Mellon University submitted a paper titled “DensePose From WiFi” to arXiv (arXiv:2301.00250). 1 The paper described a deep neural network that maps the phase and amplitude of WiFi signals to UV coordinates across 24 regions of the human body. The system reconstructs full-body human pose in real time, through walls, without a camera.
The mechanism is a property of WiFi signals called Channel State Information, or CSI. CSI is not the data transmitted over a network. It is a measurement of how the signal traveled from transmitter to receiver, capturing amplitude and phase across dozens of individual frequency channels called subcarriers, at approximately 20 samples per second. A human body moving through a room disturbs those signal paths in ways that are consistent, measurable, and recoverable. A neural network trained on those disturbances can determine where a person is, how they are positioned, and whether their chest is rising and falling.
In February 2026, a developer known as Reuven Cohen released an open-source implementation of the technique under the name RuView, also known as WiFi DensePose, on GitHub under an MIT license. 2 The repository reached the top of GitHub’s trending lists within days. The software deploys via Docker in approximately 30 seconds.
What It Actually Requires, and Why That Matters
Popular coverage has repeatedly misreported a critical technical distinction: a standard home router cannot perform this sensing. The GitHub repository states it directly. Full CSI-based pose estimation, vital sign monitoring, and through-wall detection require hardware that exposes per-subcarrier amplitude and phase data. Standard consumer WiFi equipment does not. The repository’s own documentation notes that consumer laptops “can only provide RSSI-based presence detection, which is significantly less capable.” 2
What does work is an ESP32-S3 microcontroller, a commodity chip available from consumer electronics retailers for approximately $8 to $30. A functional sensing mesh requires three to six nodes plus a transmitting router; a documented starter configuration costs approximately $54 total. Alternatively, an Intel 5300 network interface card ($15 used, with modified firmware) or an Atheros AR9580 ($20 used, with kernel patches) can perform the same function. 3
Peer-reviewed literature places the effective sensing range for commodity CSI hardware at approximately 6 to 8 meters within a single room. 4 Through-wall performance degrades with distance, but research using ESP32-S3 hardware combined with directional antennas has demonstrated activity recognition across 18.5 meters spanning five rooms. 4 A standard residential wall between adjacent units falls well within that range.
The Yagi question has a precise answer. A Yagi is a directional antenna that improves signal gain in one direction; it is relevant to transmitting or receiving radio signals, not to defending against sensing. CSI-based detection does not intercept data packets. It reads the physics of how radio waves scatter off a human body. WPA3 encryption is equally irrelevant: CSI operates at the physical layer of the radio signal, below the layer where any encryption is applied. 5 What @DoingFedTime identified correctly is that the attacker introduces their own transmitting hardware into the signal environment. The target does not need to own or operate any vulnerable device. They need only to be present inside the signal path.
One factual qualification is required before proceeding. The specific RuView/WiFi DensePose implementation has faced substantive criticism. Developers on Hacker News and GitHub identified code generating random CSI signals using np.random.rand() rather than actual hardware input, and alleged misrepresentation of cited research. Separate review flagged overnight inflation of the repository’s star count. 6 The underlying Carnegie Mellon science is a different matter entirely. The CMU paper is peer-reviewed and independently published. CSI-based human sensing has been validated across hundreds of academic studies, including a two-year evaluation spanning 16 scenarios and more than four million motion samples. The IEEE has formally standardized WiFi sensing under 802.11bf. 6 Whether this specific implementation performs as advertised is a question about one developer’s repository. Whether the underlying capability exists is not. It does.
Two Separate Legal Problems
WiFi DensePose presents two distinct legal questions requiring separate analysis. The first is what happens when a government actor deploys it. The second is what happens when anyone else does. The answers are different, and both are incomplete.
Track One: Government Actors
The Fourth Amendment stands, in the Supreme Court’s own formulation, most firmly at the threshold of the home. The Court wrote in Silverman v. United States, 365 U.S. 505 (1961): “At the very core of the Fourth Amendment stands the right of a man to retreat into his own home and there be free from unreasonable governmental intrusion.” 7 That principle has not weakened. Every major Fourth Amendment case addressing new surveillance technology in the decades since has returned to it.
The case that maps most directly onto WiFi DensePose is Kyllo v. United States, 533 U.S. 27 (2001). Federal agents used a thermal imaging device aimed at Danny Lee Kyllo’s home from a public street to identify heat patterns consistent with indoor marijuana cultivation. The Supreme Court, in a 5-4 opinion by Justice Antonin Scalia, held the surveillance was a Fourth Amendment search. The operative holding: “Where, as here, the Government uses a device that is not in general public use, to explore details of the home that would previously have been unknowable without physical intrusion, the surveillance is a ‘search’ and is presumptively unreasonable without a warrant.” 8
The majority opinion was written deliberately to reach forward. The Court declined to limit the rule to thermal imaging and warned that restricting it would “leave the homeowner at the mercy of advancing technology, including imaging technology that could discern all human activity in the home.” 8 Justice Scalia was describing a hypothetical risk. That hypothetical is now a $54 hardware kit running open-source software.
WiFi DensePose does not detect heat radiating through an exterior wall. It reconstructs body position, breathing rate, and heart rate of individuals inside the home, information that is by any defensible measure more intimate than the thermal distribution Kyllo addressed. Applied by a court willing to take the long view the majority invited, the Kyllo framework would require a warrant before government deployment of this technology against a private residence.
The open legal question is Kyllo‘s “not in general public use” qualifier. The ESP32-S3 is a $30 chip sold at consumer electronics retailers. Whether hardware costing $30, paired with a software stack available on GitHub, satisfies that threshold is a question no court has yet resolved.
A second line of authority bears on continuous monitoring. In Carpenter v. United States, 585 U.S. 296 (2018), the Supreme Court held that warrantless government acquisition of 127 days of historical cell-site location data constituted a Fourth Amendment search. Chief Justice Roberts’s majority held that “an individual maintains a legitimate expectation of privacy in the record of his physical movements,” regardless of whether the government collected the data itself or obtained it from a third party. 9 CSI-based sensing generates a continuous, real-time record of a person’s physical movements and physiological state inside a private home. Carpenter‘s logic, applied to that record, resolves in one direction.
The statutory gap remains even under the favorable constitutional reading. Title III of the Omnibus Crime Control and Safe Streets Act of 1968, codified at 18 U.S.C. § 2510 et seq., and the Foreign Intelligence Surveillance Act, 50 U.S.C. § 1801 et seq., were both designed around the interception of communications content. CSI-based sensing does not intercept communications. It reads radio wave physics. No court has ruled on whether existing statutory authority covers it. 11
Track Two: Private Actors
The Fourth Amendment constrains only government. It says nothing about what private actors can do.
There is currently no federal statute in the United States that specifically prohibits WiFi-based covert human sensing. 10 The Federal Communications Commission’s statutory mandate centers on spectrum efficiency and interference prevention, not on restricting the information that can be extracted from an authorized transmission. The Electronic Communications Privacy Act of 1986 and Title III govern the interception of the contents of wire, oral, and electronic communications. CSI-based sensing does not intercept any communication. It reads the physical behavior of radio waves as they propagate through space and interact with a human body. It operates below the layer that federal wiretapping law was written to address. 11
State law provides no consistent alternative. Some states have voyeurism or surveillance device statutes that courts might stretch to cover this conduct. None were written with through-wall CSI body mapping in mind, and most have not addressed it at all.
Any private actor who deploys an ESP32-S3 mesh and uses it to monitor body position, sleep patterns, and vital signs through a wall is operating in a legal space that existing law has not closed. GDPR, the European Union’s General Data Protection Regulation, classifies WiFi tracking identifiers as personal data, but CSI-based body pose extraction, which produces a real-time skeletal map of a specific individual inside a specific home, has not been specifically addressed by regulators on either side of the Atlantic. 12
The Question the Law Has Not Answered
WiFi DensePose is not a camera. It captures no image. It produces no recording a person would recognize as surveillance footage. What it produces is a skeletal data structure, 17 body keypoints updated 20 times per second, and a continuous stream of physiological readings. That output is invisible in the legal sense that matters most: no existing surveillance statute was written to reach it.
Traditional surveillance law was designed around evidence. A camera produces an image. A listening device produces audio. A tracking device produces location data. Each of those outputs maps onto a statutory category that legislators anticipated. CSI-based sensing produces none of them. The sensing apparatus transmits nothing detectable. The data it extracts is not something the subject ever chose to expose. It is recovered from the involuntary physics of a human body occupying a room, inside the space the constitutional order has always treated as the most protected.
In Kyllo, Justice Scalia wrote that the Court must “take the long view.” In 2001, the technology before the Court could determine whether someone was running high-intensity grow lights. The technology commercially available in 2026 can identify which room a person occupies, whether they are standing or supine, whether they are breathing at a normal rate, and what their heart rate is, through a wall, without their knowledge, for $54 in hardware. 8
The gap between those two facts is not a technical gap. It is a legislative one. And it is, at present, open.
Notes
1. Jiaqi Geng, Dong Huang, and Fernando De la Torre, “DensePose From WiFi,” arXiv:2301.00250 (submitted December 31, 2022). Available at https://arxiv.org/abs/2301.00250. Hosted by the CMU Human Sensing Laboratory.
2. RuView GitHub repository (formerly WiFi DensePose), developer Reuven Cohen (ruvnet), MIT License. Available at https://github.com/ruvnet/wifi-densepose. The repository states: “CSI-capable hardware required. Pose estimation, vital signs, and through-wall sensing rely on Channel State Information (CSI), per-subcarrier amplitude and phase data that standard consumer WiFi does not expose. You need CSI-capable hardware (ESP32-S3 or a research NIC) for full functionality. Consumer WiFi laptops can only provide RSSI-based presence detection, which is significantly less capable.”
3. On hardware costs: The repository documents a starter kit of 3-6 ESP32-S3 nodes for approximately $54. Alternative hardware includes the Intel 5300 NIC ($15 used) and Atheros AR9580 ($20 used). See also byteiota.com, “WiFi DensePose Hits GitHub #2: Real or AI-Generated Hype?” (March 2026), available at https://byteiota.com/wifi-densepose-hits-github-2-real-or-ai-generated-hype/.
4. On effective sensing range: Yaxiong Xie et al., “Commodity Wi-Fi-Based Wireless Sensing Advancements over the Past Five Years,” PMC/National Institutes of Health, available at https://pmc.ncbi.nlm.nih.gov/articles/PMC11597943/ (”The existing sensing range is usually just 6-8 m within a single room.”). For through-wall performance with directional antennas across 18.5 meters spanning five rooms, see “WiFi CSI-Based Long-Range Through-Wall Human Activity Recognition with the ESP32,” Springer Nature (2023), available at https://link.springer.com/chapter/10.1007/978-3-031-44137-0_4.
5. On the physical-layer nature of CSI and the irrelevance of encryption: Ken Imoto, “WiFi CSI: Your Router Can See You Move,” DEV Community (March 2026), available at https://dev.to/kenimo49/wifi-csi-your-router-can-see-you-move-privacy-implications-of-channel-state-information-3m5o. (”CSI operates at the Physical Layer (Layer 1) of the OSI model. Encryption protocols like WPA3 protect payloads at the Data Link Layer (Layer 2) and above. The amplitude and phase patterns of the radio waves themselves remain unchanged regardless of encryption.”)
6. On credibility questions surrounding the RuView implementation and the validity of the underlying science: byteiota.com, “WiFi DensePose Hits GitHub #2: Real or AI-Generated Hype?” (March 2026), available at https://byteiota.com/wifi-densepose-hits-github-2-real-or-ai-generated-hype/. The CMU paper has 25 citations on Semantic Scholar as of this writing. On IEEE 802.11bf standardization, see “Wi-Fi Sensing Based on IEEE 802.11bf,” NSF-funded research, available at https://par.nsf.gov/servlets/purl/10485775.
7. Silverman v. United States, 365 U.S. 505, 511 (1961).
8. Kyllo v. United States, 533 U.S. 27 (2001). Majority opinion by Justice Antonin Scalia, joined by Justices Thomas, Ginsburg, Souter, and Breyer. Decided June 11, 2001. Available at https://supreme.justia.com/cases/federal/us/533/27/ and https://www.law.cornell.edu/supct/html/99-8508.ZS.html. The operative holding appears at 533 U.S. at 40. The “long view” language and the warning about advancing imaging technology appear at 533 U.S. at 35-36.
9. Carpenter v. United States, 585 U.S. 296 (2018). Majority opinion by Chief Justice John Roberts. Decided June 22, 2018. Available at https://supreme.justia.com/cases/federal/us/585/16-402/ and https://www.law.cornell.edu/supremecourt/text/16-402. The quoted passage appears at slip op. 17.
10. On the absence of federal statutory prohibition: “Your Wi-Fi Router Could Be Watching You: How Ordinary Wireless Signals Are Being Weaponized for Mass Surveillance,” WebProNews (February 2026), available at https://www.webpronews.com/your-wi-fi-router-could-be-watching-you-how-ordinary-wireless-signals-are-being-weaponized-for-mass-surveillance/.
11. Title III of the Omnibus Crime Control and Safe Streets Act of 1968, codified as amended at 18 U.S.C. § 2510 et seq. The definition of “intercept” at 18 U.S.C. § 2510(4) covers the aural or other acquisition of the contents of wire, electronic, or oral communications. CSI-based sensing does not acquire the contents of any communication; it reads the physical propagation characteristics of radio waves. For DOJ policy guidance, see Justice Manual § 9-7.000, available at https://www.justice.gov/jm/jm-9-7000-electronic-surveillance.
12. On GDPR and the regulatory gap: Ken Imoto, supra note 5. (”GDPR already classifies WiFi tracking identifiers as personal data, yet CSI-based body pose extraction exists in a regulatory grey zone with no specific controls.”)