The search engine Shodan crawls the Internet for, among other things, Industrial Control Systems (ICS). ICS are devices used to operate and automate industrial processes. Due to the increasing popularity of the Internet, these devices are getting more and more connected to the Internet. These devices will, if not hidden, be shown on Shodan. This study uses Shodan, together with data found by other researches to plot the trends of these ICS devices. The studied trends focus on the country percentage distribution and the usage of ICS protocols. The results show that all studied countries, except the United States, have decreased their percentage of world total ICS devices. We suspect that this does not represent the real story, as companies are getting better at hiding their devices from online crawlers. Our results also show that the usage of old ICS protocols is increasing. One of the explanations is that industrial devices, running old communication protocols, are increasingly getting connected to the Internet. In addition to the trend study, we evaluate Shodan by studying the time it takes for Shodan to index one of our devices on several networks. We also study ways of avoiding detection by Shodan and show that, by using a method called port knocking, it is relatively easy for a device to hide from Shodan, but remain accessible for legitimate users.
