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--- projects:wifi_scanner [2019/11/30 13:15]
neil
+++ projects:wifi_scanner [2020/08/03 15:11] (current)
admin
@@ Line 1: / Line 1: @@
 ====== Wifi Scanner ======
+**Goals:** Two goals for this project.  I wanted to detect who was in the flat at any given time (see my [[Dynamic photo frame]] project) and I also wanted to see if I could detect spikes of activity near by (like a protest walking past the building etc).
-Basic steps.  Identify your wifi device (in my case wlp3s0), the enter monitor mode, use tcpdump to capture mac addresses and a short php script to switch between available channels:
+==== Data ====
+    * [[Projects/Wifi/Scan 1]]: First preliminary results from a full week wifi scan of my local area (11th Sep 2019 to 19th Sep 2019)
+    * [[Projects/Wifi/Scan 2]]: Full two-month scan from 1st Nov 2019 to 6th Jan 2020.  Looking for general daily activity
+    * [[Projects/Wifi/Scan 3]] - COVID-19: Are people self isolating.  Wifi activity for March 2020
+==== Setting up the hardware ====
+I have a dedicated mini PC for this.  It's sitting on the window ledge of my living room with a PCI-e 5G wifi card and multiple external antennas.
+**Basic steps:** Identify your wifi device (in my case wlp3s0), the enter monitor mode, use tcpdump to capture mac addresses and a short php script to switch between available channels:
 <code bash>
 sudo ip link set wlp3s0 down
@@ Line 26: / Line 35: @@
         usleep(200000);
         }
+}
+?>
+</code>
+===== Importing the data =====
+The raw tcpdump logs are pretty large and full of redundant information - for around a month of wifi scanning it records around 128 million lines of data (18.6Gb).
+I run the following code to simplify the logs to just pairs of the datetime (in YYYY-MM-DD HH:MM - I strip off the seconds) and the mac address (see below for the php code):
+<code bash>
+php trim.php tcpdump.log > trimmed_tcpdump.log
+</code>
+On my laptop, this processes the log files at around 300k lines/second - so in around 8 minutes.  The resulting import file is reduced to approximately 3.8 million lines.
+I created a simple mysql table to store the timestamp and mac address:
+<code sql>
+create table wifi_data (seen_time datetime, mac varchar(17), unique (seen_time,mac));
+</code>
+Then I import this directly to the mysql database using the mysql client:
+<code sql>
+load data infile 'trimmed_tcpdump.log' into table wifi_data;
+</code>
+Once I imported all the data I added an index to the mac address column:
+<code sql>
+alter table simple_data add index idx_mac(mac);
+</code>
+If you have any trouble with this command, you might want to split the file into more managable parts using ''split -l 1000000 trimmed_tcpdump.log''
+==== trim.php ====
+<code php>
+#!/usr/bin/php
+<?php
+if(empty($argv[1])) {
+    exit("Missing filename\n");
+}
+$filename = $argv[1];
+$handle = fopen($filename, "r");
+if ($handle) {
+    while (($line = fgets($handle)) !== false) {
+        $data = explode(" ", $line);
+        $datetime = date("Y-m-d H:i", strtotime($data[0]." ".substr($data[1],0, 8)));
+        $mac_addresses = preg_match_all("/(([a-fA-F0-9]{2}[:|\-]?){6}) /", $line, $matches);
+        if(is_array($matches[0])) {
+            $macs = array_unique($matches[0]);
+            foreach($macs as $mac) {
+                $mac = trim($mac);
+                $rawdata[$datetime.$mac]['datetime'] = $datetime;
+                $rawdata[$datetime.$mac]['mac'] = $mac;
+            }
+         }
+    }
+} else {
+    exit("Error opening file\n");
+}
+foreach($rawdata as $datetime=>$val) {
+    echo $val['datetime']."\t".$val['mac']."\n";
 }

neil.mckillop.org

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