“If you leave a database open on the internet, someone will find it. Over the past few weeks, hackers have targeted thousands of publicly accessible servers running database software such as MongoDB and Hadoop, and held their data for ransom.
Now someone is apparently taking matters into their owns hands, helpfully alerting admins that their databases are vulnerable to attack.”
Source: A Vigilante Is Warning Admins of Open Databases Before They Get Hacked | Motherboard