Systems and methods for scanning signatures in a string field. In one implementation, the invention provides a method for signature scanning. The method includes processing one or more signatures into one or more formats that include one or more fingerprints and one or more follow-on search data structures for each fixed-size signature or signature substring such that the number of fingerprints for each fixed-size signature or signature substring is equal to a step size for a signature scanning operation and the particular fixed-size signature or signature substring is identifiable at any location within any string fields to be scanned, receiving a particular string field, identifying any signatures included in the particular string field including scanning for the fingerprints for each scan step size and searching for the follow-on search data structures at the locations where one or more fingerprints are found, and outputting any identified signatures.