A distributed WiFi reconnaissance system using ESP32-S3 nodes and an Orange Pi as coordinator. The goal is passive RF awareness — mapping what is happening in the surrounding WiFi environment without transmitting or interacting with any networks.
Each ESP32 node scans the WiFi environment, builds structured events (not raw data), and ships them over UDP to a coordinator. The coordinator stores events to SQLite. A separate web dashboard reads the database and displays everything in real time via SSE.
The system is designed around a clear separation of concerns: nodes are dumb sensors, the Orange Pi does all storage and analysis, the browser does all rendering. No logic lives on the nodes beyond capturing and formatting events.
Practical use cases this has already demonstrated:
- Mapping every network and client device in a city-center apartment building
The two coordinator processes are intentionally separate. The ingestor has one job: receive UDP, write to DB. The dashboard has one job: read DB, serve UI. They communicate only through the database. Each is independently restartable without affecting the other.
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## Development workflow
**All coding is done on this PC.** The Orange Pi only runs the deployed files — never edit directly on it.
- Events are buffered in FreeRTOS queues and flushed once per scan cycle when back on the home channel
- If a deauth with reason code 2 is seen at RSSI ≥ -60 dBm, an alert flag triggers an immediate flush on the home channel without waiting for the next scan
-`probe_drops`, `deauth_drops`, `assoc_drops` count events lost due to queue overflow since boot. Non-zero values indicate the node is seeing more traffic than the queue sizes can absorb.
-`imp`: `high` if RSSI >= -50, `low` if <= -80, else `normal`
-`ssid` in probe events is the network the device is searching for — empty means wildcard (any network)
- Probe dedup: same MAC+SSID suppressed for 30 seconds to avoid flooding
-`wifi_rssi` in heartbeat is the node's own signal to the `sandbox` AP (not a scanned network)
- A node is considered **online** if a heartbeat arrived within the last 30 seconds; falls back to beacon within 60 seconds if no heartbeat has been received yet
### Flashing a node
Requirements: Arduino CLI v1.4.1, ESP32 core v3.3.7, FQBN `esp32:esp32:esp32s3`, user in `dialout` group.
Service files are in `coordinator/` and deployed to `/etc/systemd/system/` on the Orange Pi.
The coordinator files live at `/opt/esp32_cluster/coordinator/` on the Orange Pi.
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## Dashboard
Open `http://192.168.1.133:8080` in your browser.
### Views
- **Feed** — live beacon event stream across all nodes, capped at 100 rows, newest on top
- **Networks** — deduplicated AP table (by BSSID): times seen, best/avg RSSI, channel, encryption, node count. Sortable by any column. Each row has a ▶ button to open the RSSI history chart for that network.
- **RSSI history chart** — opens from any Networks row. Shows signal strength over time per node (1h / 2h / 6h / 24h selectable). Each node gets its own coloured line. Useful for spotting interference patterns, seeing how signal fluctuates by time of day, and comparing which node consistently hears a given AP better. Updates live as new scans arrive.
- **Cross-node** — side-by-side per-node RSSI for every AP. Shows which node is physically closer to each network. Filter to multi-node only to focus on confirmed cross-node observations.
- **Clients** — probe request data: unique MACs, vendor (OUI lookup), what SSIDs they're searching for, signal, which nodes saw them.
- **Alerts** — deauth/disassoc frame detection with four sections:
- *1h Summary strip* — total frames, deauth vs disassoc counts, unique BSSIDs and sources in the last hour
- *Most Impersonated Networks* — APs whose BSSID is being spoofed as the deauth source, ranked by frame count
- *Most Targeted Devices* — actual victim devices (by `dst` MAC), ranked by frames received across all impersonated APs
- *Detected Bursts* — fires when ≥10 frames for the same BSSID within 5 minutes. Highlighted red when confirmed by 2+ nodes. Reason code 2 at volume is the primary attack indicator.
- *Raw Feed* — last 100 deauth/disassoc events with full src/dst/BSSID/reason/RSSI detail.
- **Search** — cross-table lookup by any identifier. Supports MAC address, SSID, BSSID, and vendor name (e.g. "Raspberry", "Tuya", "Intel"). Returns all matching data across beacon, probe, and deauth tables in labelled sections. Vendor name search works by matching against the OUI database and finding all devices with those MAC prefixes.
- **Node detail** — click a node in the sidebar for stats: total events, unique SSIDs/BSSIDs, RSSI range, first/last seen, uptime, free heap, AP signal, last 100 events.
Click any node in the sidebar to open the detail view. Ten stat cards arranged in a 2×5 grid show: status, total events, unique SSIDs, unique BSSIDs, avg RSSI, first seen, last seen, uptime, free heap, and AP signal. Below the cards is a table of the last 100 events for that node.
Always visible: node list with online/offline status dot, last seen time, event count, and a compact heartbeat line (uptime · free heap · AP signal). Nodes are sorted alphabetically by node ID so the order stays fixed as more nodes are added.
A node is considered **online** if a heartbeat was received within the last 30 seconds. Falls back to beacon timestamp (60s threshold) if no heartbeat has been received yet.
Font: Roboto (Google Fonts). Chosen for readability at small sizes — the previous monospace font felt too thin at the smaller label sizes used throughout the dashboard.
SSE stream pushes new beacon events as they arrive. The feed updates immediately. All other views (sidebar, networks, chart, cross-node, presence, alerts) refresh on a 2-second debounce so a single scan burst doesn't flood the server with requests.
Networks with a blank SSID but valid BSSID, signal, and channel are **hidden networks** — APs configured not to broadcast their name. They are not hidden from passive scanners. The encryption showing as `OPEN` is a firmware parsing artifact; the network itself may be encrypted. The BSSID OUI still identifies the manufacturer.
### Probe requests and MAC randomization
Modern phones and laptops (iOS since ~2020, Android since ~2021) randomize their MAC address for probe requests. A randomized MAC has bit 1 of the first byte set — the dashboard detects this and labels it "Randomized MAC" instead of doing a meaningless OUI lookup.
What probe data tells you:
- **Directed probes** (with SSID): the device has connected to that network in the past
- **Wildcard probes** (empty SSID): the device is searching for any available network
- Probe data maps **client devices**, not infrastructure — complementary to beacon scan data
The raw deauth feed in the Alerts tab will fill up constantly — deauth and disassoc frames are a normal part of WiFi operation (devices disconnecting, APs doing band steering, power saving). This is expected and not cause for concern.
The **Bursts** section is the anomaly detector. A single unique source MAC generating 10+ deauth frames for the same BSSID within 5 minutes is not normal operation — it indicates a deauth flood, the standard precursor to a WPA2 handshake capture attack. The attacker forces connected clients to disconnect, captures the 4-way handshake when they reconnect, and then cracks it offline.
Multi-node confirmation (`node_count > 1`, highlighted red) significantly raises confidence — it means the source is physically close and strong, not a distant weak signal.
| `sandbox` | 2.4GHz | Main network, nodes connect here|
| `botnet` | 2.4GHz | IoT devices |
| `pronet` | 5GHz | Main 5GHz network |
| `mango` | 2.4GHz | Secondary network |
`sandbox` BSSID `1C:3B:F3:9C:AC:30` appearing in deauth/impersonation data is expected — our own nodes briefly deauth from it during channel hopping and reconnect.
The `oui.txt` file is the IEEE public OUI database (39,171 entries as of download). It maps the first 3 bytes of a real MAC to a manufacturer name. Used in the Clients tab. Refresh it occasionally by re-running `deploy.sh` after downloading a fresh copy from `https://standards-oui.ieee.org/oui/oui.txt`.
A persistent automated deauth flood has been running since **2026-04-03**, targeting `38:2C:E5:7E:77:1D` (Tuya Smart Inc. device). Four spoofed source MACs fire simultaneously roughly every hour, all using reason code 2, impersonating real AP BSSIDs in the building. All 4 nodes confirm it. Consistent with an automated WPA2 handshake capture tool. No action taken yet — being passively monitored.
SSID: `Living Room speaker.n078` · BSSID: `FA:8F:CA:76:06:B2` · ch 6 · OPEN · RSSI -54 dBm (bathroom, same apartment).
Broadcasting an open unauthenticated hotspot. Next step: connect via Parrot laptop + Alfa adapter, nmap the provisioning interface, document what is exposed. Not yet started.
Tab switches took up to a minute to load. The Networks tab failed to load entirely. The SSE live feed would stall during tab switches. The root cause was three compounding issues:
**1. Blocking the async event loop.**
FastAPI routes are `async def`, but the SQLite calls (`sqlite3` module) are fully synchronous. When called directly inside `async def`, they block uvicorn's entire event loop — meaning while one slow query runs, the server cannot serve any other request, including the SSE stream. This is why everything froze together.
**2. Expensive endpoints had no caching.**
`/api/alerts`, `/api/sessions`, `/api/presence`, and `/api/cross-node` ran full database queries on every single request, with no result caching. The 2-second debounce on the frontend meant these were being called repeatedly.
`build_sessions()` was the worst: it pulled every deauth event from the last 30 days and grouped them into sessions in a Python loop — O(N) in Python on every call, with no cache. Under a sustained deauth flood (thousands of events/day), this was very slow.
`build_alerts()` ran several queries against the **entire**`deauth_events` table with no time cutoff — top targets, top targeted devices, reason breakdown, activity heatmap all scanned all-time data.
**3. Unbounded database growth.**
No pruning meant every query got slower every day as the tables grew. The database had also developed B-tree corruption (double-referenced pages, out-of-order rowids), likely from WAL journal not checkpointing cleanly under sustained write load. The database was rebuilt clean.
### Fixes applied
- **`asyncio.to_thread()`** — all `build_*` calls in every route are now dispatched to a thread pool executor. The event loop stays free to handle SSE and other requests while queries run in the background. The SSE generator's inline `query()` calls were also fixed the same way.
- **Caching added** — alerts (60s TTL), sessions (60s), presence (60s), cross-node (60s) now cache results in memory. The existing nodes/networks/clients caches were kept. Tab switches hit the cache on repeated loads rather than re-querying the DB.
- **Time bounds on alerts queries** — top targets, top targeted devices, reason breakdown, and activity heatmap are now scoped to the last 7 days instead of all-time. Still meaningful, no longer scanning the full table history.
- **Composite indexes added** — added `(bssid, received_at)` on `beacon_events` and `deauth_events`, and `(src_mac, received_at)` on `probe_events`. Queries that filter by time and aggregate by BSSID or MAC now use a single composite index instead of two separate ones.
- **Background pruning task** — at startup, a background coroutine runs every 6 hours and deletes rows older than `HOT_DAYS` (30 days) from all event tables, followed by a WAL checkpoint. The database will no longer grow indefinitely.
