A New York-based app called Twitter Audit runs a scan of the accounts following any Twitter handle. It calculates whether the first 5,000 accounts it scans are managed by live humans, then takes an educated guess at the full ratio of real followers to bots. "Of course, this scoring method is not perfect," the app's creators admit, "but it is a good way to tell if someone with lots of followers is likely to have increased their follower count by inorganic, fraudulent or dishonest means."