Fingerprinting (DLP) is a technique where DLP systems capture structural characteristics (a digital fingerprint) of documents to recognize them even after modifications. Even when text is copied, reformatted, or pasted into other documents, the system identifies the content by its fingerprint.
Fingerprinting is particularly suited for unstructured data such as contracts, engineering drawings, or source code. It complements rule-based DLP approaches (e.g., regular expressions for credit card numbers) that only work with structured data patterns. In practice, the documents to be protected are registered once (enrollment), after which the system monitors all output channels for matches.