It was only a matter of time until the first queries for tools like https://www.shodan.io to search for Home Assistant instances showed up.
To get an idea about how your Home Assistant instance looks to a network scanner, you can use
nmap tool is already available if you are using the nmap device tracker.
$ nmap -sV -p 8123 --script=http-title,http-headers 192.168.1.3 Starting Nmap 7.12 ( https://nmap.org ) at 2016-10-06 10:01 CEST Nmap scan report for 192.168.1.3 (192.168.1.3) Host is up (0.00011s latency). PORT STATE SERVICE VERSION 8123/tcp open http CherryPy wsgiserver | http-headers: | Content-Type: text/html; charset=utf-8 | Content-Length: 4309 | Connection: close | Date: Thu, 06 Oct 2016 08:01:31 GMT | Server: Home Assistant | |_ (Request type: GET) |_http-server-header: Home Assistant |_http-title: Home Assistant Service detection performed. Please report any incorrect results at https://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 6.70 seconds