Digital signs in Brookline are collecting data from your phone as you walk by

Original Article ↗ Hacker News Discussion ↗

Technical details: MAC/BLE and tracking

  • Discussion centers on what is actually collected: Wi‑Fi/Bluetooth MAC addresses, possibly hashed/encrypted, and the claim about “IP addresses,” which several say is technically wrong since phones don’t associate as clients.
  • BLE uses “resolvable private addresses” derived from a device secret; random observers can’t map them back to identity, but paired devices can.
  • Modern iOS/Android do MAC randomization: per‑SSID persistent random MAC when joined, and frequently changing random MACs when just scanning.

Effectiveness and privacy risk

  • Many argue randomized MACs turn this into coarse footfall counting, not long‑term individual tracking.
  • Others counter that even pseudonymous MACs are personally identifiable if stable over a short period or combined with other signals (e.g., SSID probes, other static devices).
  • One point: the real threat surface is often elsewhere (apps, big platforms, carrier data) rather than a streetside sign.

Legal, policy, and transparency

  • Some see this as mild “data exhaust”; others as government‑adjacent surveillance that should be FOIA‑able and publicly auditable.
  • One commenter has already filed a FOIA request for all collected data and contracts and plans to publish it.
  • There’s debate over whether such data should even be collected if the municipality doesn’t actively use it.

Utility vs “privacy theater”

  • Supporters liken it to an automated people counter that helps with urban planning and ad impression estimates, arguably less intrusive than cameras or facial recognition.
  • Skeptics say city officials apparently don’t find the data useful, suggesting the main value is to the vendor and advertisers.

Circumvention and countermeasures

  • Some advocate simple avoidance: turn off Wi‑Fi/Bluetooth, use airplane mode, or rely on MAC randomization.
  • Others propose “data poisoning” by flooding kiosks with fake MACs using laptops, Pis, or replayed captures, to degrade dataset quality.

Device behavior and usability tensions

  • iOS behavior around turning Wi‑Fi/Bluetooth truly off is contentious; some report it silently re‑enables, others don’t.
  • Workarounds via automation/Shortcuts are suggested, but criticized as user‑hostile when “off” doesn’t stay off.
  • Broader theme: accumulated distrust in tech companies leads some users to prefer extreme measures (airplane mode, Faraday bags) over partial mitigations.