It wouldn't require extravagant effort or even new technology. The open-source Honeynet Project created honeytokens as an integral part of its trap-the-intruder strategy in 2003.
Honeytokens are good tools for tracing and proving the ownership of data because they can be created to be unique and embedded within almost any set of protected data.
They're completely separate entities, with no real value of their own except a unique identifier the owner can use to track them down. They could be fake credit-card records in a database, for example, that could be used later to identify a data set incontrovertibly as one stolen from the facility that installed the fake record.
Here's the original description of honeytokens from Lance Spitzner, founder of the Honeynet Project, from 2003.
In calling them "the other honeypot, " Spitzner made them easy to understand, but limited their applicability.
As a digital honeypot, honeytokens could be stolen without cost to the owner, and used to locate or identify stolen data.
They couldn't phone home effectively because their streams of packets got lost in all the other billions of packets that all looked like normal Internet traffic.
Adding greater communications ability to honeytokens and salting them into data sets that are either vulnerable to theft or likely to be attacked builds into the crooks' payload a beacon that can call back to the owners to let it know where it's been taken.
Smarter honeytokens don't require the kind of full-database or record-by-record containerization as would attempts to secure every data bit, and they wouldnt' be so small and stupid they couldn't get their messages through.
If, as Pentagon cybersecurity planners recently acknowledged, it's basically impossible to keep determined hackers out of your network and better to build a stiff firewall and add the ability to detect and counter intruders once they've penetrated, smart honeytokens offer a third line of defense – not stopping data thieves, but making it possible to catch them after they've gotten the data back to where it's going.
source: Honeynet Project