DHCP fingerprinting is a method of determining an operating system using only the broadcast packets it sends as part of a DHCP transaction. DHCP fingerprinting unique in that it is ubiquitous, accurate, and totally passive. As an added benefit, the DHCP relay functionality present on most networks acts as a built-in probe. It was initially described in Next Generation DHCP Deployments (SysAdmin, February 2005) by Dave Hull and George Willard and is now found in a small number of open-source and commercial products. Please see the related projects section for a few such implementations.

FingerBank aims to act as a central repository for DHCP fingerprint data and allow users to submit, search, and export it in a format tailored to their tool of choice.