Forum: µC & Digital Electronics ESP8266 "calling home"

von Jo (Guest)

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NOTE: This is a translation of my German post 'ESP8266 "telefoniert nach 
Hause"' in mikrocontroller.net. I translated it to reach a broader and 
more international audience.

Back in october/november I build a light sensor to control the lighting 
around my house. You can see the result in the attached picture and the 
sensor works fine. The ESP8266 is connected to a WLAN, that is not 
connected to the internet and is utilized only for local traffic. Then I 
got a new router and noticed, that the ESP8266 tries to reach an 
external IP address (now, two weeks ago it was The ESP8266 scans ports in the upper port range from 
about port 30.000 to 62.000 on that specific address.

Until I noticed the described behaviour, the ESP8266 was not capable to 
communicate with external (internet) IP addresses. I can rule out that 
the ESP8266 responds to incoming traffic from the internet. I changed 
that now and currently I am sniffing the traffic. An actual log of this 
traffic is attached as a PCAP-File, which you can download for the use 
in Wireshark.

My device is an ESP8266 coupled with an I2C BH1750 light sensor. The 
ESP8266 contains portions of the „ESP8266AdvancedWebserver“ example of 
the Aruino IDE (1.6.4) plugin, which was installed through the 
board-manager. The webserver returns the sensor value upon a http 

I have coded the ESP myself via Arduino IDE and scanned the libs 
available as source code. I did not find anything that could explain the 

I have made use of the following libs:

#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>
#include <ESP8266mDNS.h>
#include <Wire.h>
#include <math.h>

At the moment I cannot re-enact this situation in lab conditions and 
with different releases. Hence, I kindly ask you to check if your 
ESP8266 is calling home as well. You just need to check the routing 
table of your router.

Please post if your ESP8266 connects to "alien" servers as well. 
Positive/negative reports are welcome.

I attached a picture of my light-sensor, screenshots of my routing table 
and a pcap file for Wireshark, where I have collected a few of the 
suspicous pakets.

I look forward to hearing from you,

von stefan us (Guest)

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It turned out that the issue was caused by the application itself (not 
the ESP module or firmware).  What seemed like "calling home" are really 
random data.

von Chris Tuff (Guest)

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What do you mean by "random data?" I have two that are doing the exact 
same thing.

von bmcniel (Guest)

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Call me one of those conspiracy nuts, but one of those IP addresses is 
in China. Think about this, you're making these tiny controllers that 
are made to connect to wireless LANs and likely the internet. You make 
these and sell them for a couple bucks and half a bazillion are sold and 
being tinkered with everywhere. You have 1) a massive source of data 
that could be harvested with no effort, and 2) a controller that can be 
triggered to perform a simple function. We really don't know what is in 
the chip. They may have inaccessible memory that has a tiny program to 
phone home and do something. I'm just sayin....

Am I off my rocker? Has my cheese slipped off my cracker?

Has anyone read "Daemon" by Daniel Suarez?

Awesome book. You would definitely be interested.

von B. Spitzer (Guest)

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Configure your router to cut the ESP from external connections. If you 
need access from thr global internet, use an Rpi to handle the data or 
use VPN.


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