New court documents obtained by the American Civil Liberties Union include an FBI affidavit describing the agency’s plan to run 23 child pornography websites on the so-called “darkweb.” Those sites, seized rather than created by the agency, were then to be used to infect visitors’ computers with a malware-like exploit. The sites were accessed through the normally anonymous Tor system, but the government malware forced Tor browsers to provide detailed information on visitors to investigators. According to the documents, the sites could have been hosted on government servers for as long as 30 days.

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The documents, originally reported and distributed by Ars Technica, show a broadened scope for a method used in 2015 to target visitors to a single seized site. The 2015 investigation led to dozens of prosecutions of the site’s users.

However, legal experts have expressed serious concerns about various precedents being set by these investigations, particularly regarding judges’ ability to approve searches outside of their jurisdiction. Several judges in resulting cases have ruled the initial warrant invalid because searches reached across jurisdictions without proper authorization. In some cases, judges threw out evidence gained through the method.

The ACLU is paying close attention to the issue because an imminent change to the relevant rule could relax the jurisdictional limits on warrants for remote searches. In early 2015, Google voiced its opposition to the change, saying it threatened “to undermine the privacy rights and computer security of Internet users.” Oregon Senator Ron Wyden has also said he opposes the rule change, but there currently seems little chance it will be blocked before going into effect on December 1st.

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Those aren’t the only concerns about the investigation. The FBI’s remote searches in the initial case reached outside of U.S. borders, which some legal experts say could erode national sovereignty and threaten U.S. foreign relations.