Law enforcement authorities have been planting their own nodes to Freenet in order to track down cyber criminals on the network. Freenet is an anonymous P2P network, which routes traffic using multiple nodes to hide the location of the users when they share files. Freenet is, by the way, often quoted by the media as part of the dark web since its efforts for anonymization. However, currently, it appears that the network has been under police surveillance.
Court records state that in the case of Paul Bradley Meagher, a University of Dakota police officer who was arrested for downloading child porn from Freenet, the North Dakota Bureau of Criminal Investigation had been running an undercover operation in the network since 2011, planting their own nodes in the P2P file sharing service. With this done, the law enforcement authorities were able to log the IP of the users they surveyed and track them down, so the police knowing the locations of the targeted people, making them able to arrest them.
A Dakota student news site describes how, in the charge of the case, Investigating Officer Jesse Smith managed to acquire the laptop of Bradley, which was still running Freenet on