More than 16,000 signals are analyzed by a service called Sift, which generates a "Sift score" ranging from 1 – 100. The score is used to flag devices, credit cards and accounts that a vendor may want to block based on a person or entity's overall "trustworthiness" score, according to a company spokeswoman.

From the Sift website: "Each time we get an event — be it a page view or an API event — we extract features related to those events and compute the Sift Score. These features are then weighed based on fraud we've seen both on your site and within our global network, and determine a user's Score. There are features that can negatively impact a Score as well as ones which have a positive impact."

Factors which contribute to one's Sift score (per the WSJ):

Is the account new?

• Are there are a lot of digits at the end of an email address?

• Is the transaction coming from an IP address that's unusual for your account?

• Is the transaction coming from a region where there are a lot of hackers, such as China, Russia or Eastern Europe?