Vendors of trade surveillance software are not generally regarded as quasi-godly entities. They scrutinize their customers’ transactions, and send alerts—often, too many alerts—when something anomalous is spotted. Perhaps a trader is using inside information, spoofing, or hiding losses. Most of the time, the trader will be doing nothing untoward at all.

But that describes a vendor’s work with an individual client. What about the vast trove of data that is created when all of those clients are