Recent protests at the Immigration and Customs Enforcement (ICE) facility in Portland have raised serious concerns regarding the surveillance of protesters’ identifiable information from their cellphones. This alarming conclusion emerged from an in-depth analysis conducted by Straight Arrow News, which indicates that a cell-site simulator may have been employed in the vicinity of the protests.
Mikhail Thalen, a tech reporter for Straight Arrow News, joined OPB’s “Think Out Loud” during a segment on Wednesday to elaborate on his findings and the technology used in the investigation. To grasp the implications of his discoveries, it is crucial to understand how cellphones typically interact with nearby cell towers for signal connection.
When a cellphone is powered on, it searches for the strongest signal by connecting to the nearest cell tower. This connection process involves transmitting a unique International Mobile Subscriber Identity (IMSI), a 15-digit code linked to the phone’s SIM card, allowing the network to identify the user. Once the tower records the IMSI, it assigns a temporary one that changes as the phone connects to different towers to enhance user privacy and prevent consistent tracking.
However, the use of a cell-site simulator poses a direct threat to this privacy. These surveillance devices mimic legitimate cell towers and can obtain considerable information by forcing phones in the area to connect to them, effectively capturing IMSIs. These simulators can be portable, hidden in backpacks, installed in vehicles, or even positioned on aircraft.
Regular cellphone users are unlikely to realize if their devices have connected to such a fake tower as there are no obvious indicators of this kind of surveillance. Thalen introduced a specialized device called Marlin, a software-defined radio discovering various wireless signals, which he utilized to scrutinize technology at the ICE facility.
The Marlin tool was developed by researchers from the University of Florida and ETH Zürich after dedicating 400 hours to track cellular signals across two continents. According to their findings, legitimate cell towers typically request an IMSI in less than 3% of interactions, with occasional spikes reaching no higher than 14%. During Thalen’s visit to the ICE facility, he recorded a significant increase in requests for IMSI, witnessing multiple spikes as high as 18%.
Interestingly, when he moved to a nearby hotel about 1,500 feet away from the facility, the percentages of requests returned to more typical levels, suggesting that the heightened activity was potentially localized to the ICE site.
While this data does not serve as concrete proof of surveillance, it raises significant questions about the potential use of cell-site simulators at the ICE facility during a time marked by heightened tensions and protests surrounding its operations. Thalen attempted to reach out to ICE and the Department of Homeland Security for comments regarding his findings but encountered silence from these agencies. The Portland Police stated they had not deployed any simulators and suggested contacting federal authorities.
Past investigative documents, however, reveal a troubling history of ICE’s use of cell-site simulators. According to records obtained by the ACLU in 2020, ICE employed these devices at least 466 times between 2017 and 2019. Furthermore, a recently unsealed warrant indicated the agency utilized a simulator in Utah in August 2023 to locate an individual ordered to leave the U.S.
Moreover, financial documentation shows that in May, ICE procured $825,000 worth of vehicles equipped with cell-site simulators and currently maintains a $4 million contract with a defense contractor that manufactures these technologies. In a follow-up investigation, Thalen discovered similar anomalous data outside another ICE facility in Washington state, prompting plans to continue examining other protest locations.
Often, the use of cell-site simulators by law enforcement is to collect IMSI data to map movements and interactions of individuals. Law enforcement agencies may also leverage these devices in more targeted operations to track specific individuals. In these scenarios, authorities can obtain an individual’s phone number and request information from the phone’s service provider, thereby linking the IMSI to a specific person.
Despite this operational handling, the collection of IMSI data raises privacy concerns as multiple devices connect to the system during the examination. While law enforcement argues they don’t retain the information from these extraneous devices, the potential for misuse and surveillance looms large.
Thalen emphasized that the extent of information harvested from IMSI data alone can vary. Authorities can potentially use this data to establish movements, interactions, and activities of individuals in a given area. For instance, they could map movement patterns to identify common visitors or isolate unique, infrequent presences at a protest. If law enforcement arrests an individual during such an event, they could trace that person’s history of movements based on the associated IMSI.
Furthermore, the technology behind cell-site simulators extends to intercepting communications, including text messages and voice calls if they are unencrypted. Individuals using encryption apps like Signal might not be at risk, as these messages remain secure and undiscoverable during transmission.
To mitigate risks associated with cellphone surveillance, Thalen recommends minimizing reliance on cellular devices in protest settings. For those participating in such activities, putting phones in airplane mode or utilizing security measures like disabling the 2G connection can be beneficial. The 2G system remains insecure and can be exploited by simulators.
Moreover, users should consider alternative methods, such as keeping a ‘burner’ phone with limited data for contact during protests. Thalen touched on the emergence of new technologies capable of rotating IMSIs at set intervals to enhance user privacy but acknowledged that such measures may be impractical for the average person. Ultimately, the conversation around surveillance at protest sites underscores the need for increased awareness of potential privacy violations and the extent of digital surveillance capabilities employed by law enforcement agencies.
image source from：opb
