  Efficient and reliable automated detection of modified image and multimedia
files has long been a challenge for law enforcement, compounded by the harm
caused by repeated exposure to psychologically harmful materials. In August
2019 Facebook open-sourced their PDQ and TMK + PDQF algorithms for image and
video similarity measurement, respectively. In this report, we review the
algorithms' performance on detecting commonly encountered transformations on
real-world case data, sourced from contemporary investigations. We also provide
a reference implementation to demonstrate the potential application and
integration of such algorithms within existing law enforcement systems.
