SignalTrace pairs wireless device signals with license plate records

A surveillance technology designed to correlate wireless signals emitted by phones, smartwatches and other electronic devices with automatic license plate reader observations is being relaunched as SignalTrace, raising fresh questions about whether supposedly anonymous device signatures can become a new form of persistent identity.

Leonardo U.S. Cyber & Security Solutions says SignalTrace is the next evolution of technology previously marketed as EOC Plus. Rather than identifying people directly, the system correlates Bluetooth, Wi-Fi, RFID and other wireless signals with nearby vehicles to build what the company describes as recurring electronic fingerprints.

Those fingerprints can then be associated with specific license plates, allowing investigators to recognize vehicles even when plates are removed, altered or obscured and potentially reconstruct patterns of movement from repeated observations.

Leonardo says strategically placed sensors can detect Bluetooth, Wi-Fi, supported radio frequency identification (RFID) and other wireless signals from devices in or near passing vehicles. The observations can then be analyzed through the company’s Enterprise Operations Center platform.

Rather than treating each detection in isolation, the system looks for groups of devices that repeatedly appear together. Leonardo describes the resulting combination as an “electronic fingerprint.”

When wireless sensors and a license plate reader observe the same traffic, their time and location records can be correlated to associate a recurring fingerprint with a particular vehicle and license plate.

Leonardo says that could help police recognize a vehicle when its plate has been removed, obscured, altered or replaced. It also says recurring signatures can reveal travel patterns, convoys or signatures appearing with different vehicles.

SignalTrace can operate without a plate reader at every collection point. Leonardo’s product page says it can also be used in subways, malls and other off-road settings, extending its potential reach from vehicles to people carrying devices through public spaces.

The company says SignalTrace does not decrypt or read device contents, access communications or retrieve information stored on personal devices. Unlike a cell site simulator, it is not described as impersonating a cellular tower or forcing phones to connect.

Its utility instead comes from detecting information exposed through wireless emissions, recording where and when it appeared and correlating repeated observations with other data.

From anonymous signals to identifiable people

That distinction is central to Leonardo’s privacy defense but does not resolve whether the resulting information can become identifying.

In announcing the renamed product, Leonardo said SignalTrace creates “anonymous electronic signatures” and “does not identify individuals.”

A 2024 release announcing its first patent was less restrained, describing EOC Plus as a system intended to help law enforcement identify people of interest through signatures emitted by their devices.

Leonardo received U.S. Patent 11,941,716 on March 26, 2024. The U.S. Patent and Trademark Office issued continuation patent 12,614,241 on April 28, 2026.

The latter describes correlating electronic signatures from devices with visual identifiers, searching for those signatures where a visual identifier is not captured and generating records of a target’s movements or location patterns.

A wireless signal does not need to contain a subscriber’s name to become identifying. The same signature might repeatedly appear with a car registered to one person, outside that person’s home or beside another device associated with a known subject.

The National Institute of Standards and Technology defines personally identifiable information to include information that can distinguish or trace someone when combined with other linked or linkable data.

That definition does not determine SignalTrace’s legal status, but it is broader than the proposition that data remains anonymous unless it contains a person’s name.

That is the central concern raised by Indiana University researcher Nicole M. Bennett in an analysis published by The Conversation. Police could begin with a nameless pattern, use repeated movements and associations to narrow the field and only then attach identities to the people involved, Bennett said.

The process could also implicate passengers, people sharing a commute or pedestrians near a sensor.

A recurring association shows that devices were observed near one another. It does not establish why they were together, who possessed each device or whether the same person carried it on every occasion.

Questions about deployment have become more complicated since SignalTrace first drew wider attention in June.

Questions over deployment and accuracy

Security engineer Ryan O’Horo said he identified four apparent installations along Oxon Hill Road and National Harbor Boulevard in Oxon Hill, Maryland. One set of antennas is near a Flock Safety plate reader, while another is co-located with Leonardo PlateHunter 900 cameras.

O’Horo subsequently identified another apparent installation in Solomons, Maryland.

The identifications are based on public street imagery, apparent hardware characteristics and comparisons with Leonardo’s promotional photographs.

Neither the equipment’s identity nor its operational status has been confirmed through agency records, and the sites should not be considered as confirmed SignalTrace deployments.

O’Horo said imagery showing equipment resembling the system at the National Harbor location dates to May 2022.

Leonardo told Forbes in 2024 that it had no paying customers and that one customer was testing the technology in an environment not being used to surveil the public. The images alone cannot establish whether the equipment was active, what it collected or whether any information was retained or used.

O’Horo’s analysis also identified limitations in what the visible hardware can probably accomplish. Devices do not continuously transmit stable identifiers.

Newer phones and computers frequently randomize addresses exposed through Wi-Fi and Bluetooth, while transmissions occur intermittently across different channels.

A directional antenna also cannot conclusively determine which nearby vehicle contained a detected device. Signals from pedestrians, cyclists and adjacent lanes could be collected during the same period.

SignalTrace appears to depend on repeated encounters and software-generated correlation scores that investigators must interpret.

Protection is uneven, however. Earbuds, vehicle infotainment systems and other connected products may expose persistent identifiers or recognizable device names more readily than newer phones.

O’Horo concluded that the observed configuration could probably collect some Wi-Fi and Bluetooth data and certain 915 MHz RFID signals, but not necessarily every category advertised in earlier materials.

No publicly available independent evaluation has established SignalTrace’s accuracy or false-association rate.

 A new surveillance model emerges

Leonardo is not alone in pursuing the technology. Webb and Val Verde counties in Texas acquired Jenoptik’s TraffiCatch, which was marketed as combining plate recognition with Wi-Fi and Bluetooth identifiers. The purchases used federal Operation Stonegarden and Texas Operation Lone Star funding.

Operation Stonegarden is a FEMA grant program that funds state, local, tribal and territorial law enforcement cooperation with Customs and Border Protection on border security operations.

Customs and Border Protection also awarded Weathered Security a $227,500 purchase order in 2021 for radio-frequency sensor nodes for the Border Patrol Tactical Unit.

Together, these systems point to a broader shift in surveillance technology. Rather than beginning with a known person or license plate, investigators can start with recurring wireless signatures, patterns of movement and device associations, then combine those observations with license plate, location and other records to work backward toward identity.

Article Topics

ANPR  |  device fingerprinting  |  license plate readers  |  SignalTrace  |  surveillance