A federal court in Massachusetts, in U.S. v. Levin, ordered the suppression of evidence that the FBI had obtained with a warrant authorizing the use of a “network investigative technique” (NIT) to hack a child porn website and collect evidence from the computers of users. The website, Playpen, was accessible to users only through the “Tor” network, which is designed to preserve users’ anonymity by masking their IP addresses. The FBI had seized the website’s server, which was located in Virginia. But instead of shutting it down, the FBI continued to run the site for several weeks, obtaining a warrant from a federal magistrate judge in Virginia to use the NIT to collect evidence on visitors to the site. Specifically, the NIT covertly transmitted code to the computers of users of the website that caused the users’ computers to transmit information back to the government-operated server, including the users’ IP addresses. The court found that the warrant was invalid because it authorized the search of computers that turned out to be outside the magistrate’s district (in the defendant’s case, the computer was in Massachusetts) and thus violated the territorial restrictions on the magistrate’s authority. The ruling, if followed by other courts, may make it more difficult for the FBI to conduct remote searches of computers whose location is unknown at the time of the search.