Many MongoDB administrators have exposed 595.2 terabytes of data by using bad poor configurations, or un-patched versions of the MongoDB. John Matherly argues that around 30,000 databases are exposed because administrators are using old versions of MongoDB, and these old versions fail to bind to localhost. Most of the exposed DB are running in the cloud, hosted in Amazon, Digital Ocean, and in services such the referred ones, such as Digital Ocean. In February 2015 nearly 40,000 entities running MongoDB were found vulnerable to cyber attacks.”]
Source: http://securityaffairs.co/wordpress/38734/hacking/mongodb-600-tb-exposed.html