Methodology

Query OpenCelliD (free key at opencellid.org) to map towers within a 0.5–5km radius

Suspicion indicators: isolated 2G/GSM tower in LTE-heavy area (downgrade attack), <5 observations, range > 5km, unknown MCC/MNC

Without key: educational content + links to AIMSICD (Android), SnoopSnitch, PCell Info

Sources: OpenCelliD, GSMA FS.11, Positive Technologies research, Mozilla Location Services