People love storing information in databases, because databases make it easy to store, sort, and search large amounts of data. Sometimes those databases are not as secure as they should be.
Traditional databases are great for storing structured data, like a list of books. Books are sort of uniform, in that you describe books pretty well with a small set of identifiers (like title, ISBN, author, year of publication, publisher, etc.), and those identifiers don’t change a lot over time or from book to book. A spreadsheet will often suffice for this kind of thing.
Describing people is harder, because people are weird. Consider medical records. Women would need lots of columns men don’t need, and vice versa. A patient with diabetes would have lots of columns not relevant to a non-diabetic. Likewise for a cancer patient.
A relatively new class of database called NoSQL is good at storing records on people and other complicated subjects, because NoSQL databases can store (and sort and search) unstructured data. MongoDB is a popular open-source NoSQL database product.
The idea is that a company installs MongoDB on their server, pours data into it, and writes a web application (or some other kind of interface) to access the data. Earlier versions of MongoDB had some poorly-chosen default settings which would make the database itself directly available over network connections. More recent versions of the software have better defaults, but the damage is done: lots of people installed MongoDB with the network-available default, and they never changed it.
So even if they wrote a web application with good access controls, the database itself might be open to the internet. If the database’s network port wasn’t firewalled, anyone could completely bypass the web application’s access restrictions by connecting directly to the database (and they could download as much data as they wanted).
It’s important to note that this problem is not specific to MongoDB. This could happen with any network-enabled database system. But because of some recent discoveries of internet-accessible MongoDB databases, they’re in the spotlight. The Office of Inadequate Security has reported on several high-profile examples of open MongoDB databases, including a voter registration database with 191 million records. A security researcher named Chris Vickery used Shodan to find these databases.
That bears repeating: an ordinary guy used a search engine to find a database with the voter registration data of 191 million Americans.
All too often people don’t take care of their data. The Office of Inadequate Security reports on data breaches large and small all the time. Sometimes it’s 191 million voter records over a network connection, and sometimes it’s patient records left on a sidewalk next to a trash can when a doctor’s office goes out of business. That site might be a good place to look for inspiration when you’re writing a character that needs to acquire data that wouldn’t (or shouldn’t) be widely available. Whether your character needs to do some port scanning or some dumpster diving, she might be able to get her hands on all kinds of data.