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Privacy September 8, 2026

SDR Counter-Surveillance: $30 Bug Detection

Software-Defined Radio (SDR) replaces traditional hardware radio components with software. For $30, an RTL-SDR dongle connected to your computer or phone can monitor radio frequencies used by surveillance devices.

What SDR can detect

WiFi cameras: Hidden cameras that transmit over WiFi (2.4 GHz or 5 GHz) produce detectable RF signatures. An SDR can identify unexpected WiFi transmissions in a room.

Audio bugs: Many audio transmitters operate on common frequencies (315 MHz, 433 MHz, 915 MHz ISM bands). SDR can scan these bands for unexpected transmissions.

Cellular transmitters: Hidden cameras and bugs that use cellular data produce detectable 4G/5G signals. SDR can identify unexpected cellular transmissions.

Cell-site simulators (Stingrays): These devices create anomalous cell tower behavior detectable by monitoring cellular frequencies. Unexpected tower appearances, 2G downgrade attempts, and signal strength inconsistencies are indicators.

Bluetooth trackers: While BLE operates at 2.4 GHz, SDR with appropriate software can detect and identify Bluetooth Low Energy devices broadcasting in an area.

GPS trackers: Active GPS trackers that report via cellular create detectable RF emissions. Passive GPS loggers don’t transmit and aren’t detectable by SDR.

Getting started

Hardware needed:

  • RTL-SDR V3 dongle ($30)
  • Antenna (included with most kits)
  • Computer or Android phone with USB OTG

Software options:

  • SDR# (Windows): General-purpose SDR receiver
  • GQRX (Linux/Mac): Open-source SDR receiver
  • RTL-SDR Scanner: Automated frequency scanning
  • DroneWatch (Symvek, in development): Purpose-built counter-surveillance SDR application

Limitations

SDR detection is passive (receive-only, completely legal). But:

  • Requires knowledge of what frequencies to monitor
  • Short-range devices may only transmit intermittently
  • Identifying surveillance devices among normal RF traffic requires training
  • Professional TSCM equipment is more capable (but costs $5K-$50K)

What Symvek is building

The direction this is heading is automated SDR-based counter-surveillance: connect an RTL-SDR, and signal analysis flags transmissions worth a second look. The hardware is already cheap enough; the gap is in the analysis.

Start with understanding your area’s fixed surveillance on Sentinel, then add SDR-based detection for hidden devices.

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