From the register:
A ruling by a US federal judge could unravel as many as 1,200 criminal prosecutions of alleged pedophiles by the FBI.
Massachusetts District Court Judge William Young today declared that the magistrate judge who issued a warrant authorizing the FBI to infect suspects' PCs with tracking malware lacked the proper authority to do so.
In early 2015, the Feds had used the warrant to install a so-called NIT – a Network Investigative Technique – on the computers of people who visited a website hidden in the Tor network that hosted a huge archive of photos and videos of child sex abuse.
The agents commandeered the website's server, and before shutting it down, configured it to deliver the NIT to perverts' PCs for a couple of weeks, allowing investigators to unmask and identify the website's visitors even though they were connecting via the anonymizing Tor network. Each NIT, once in place on a computer, was able to ping an outside FBI-controlled system to reveal a suspect's true public IP address, which could be traced back to their home with their ISP's help.
Hundreds of machines visiting the hidden Playpen website were infected by the FBI's NIT. However, it turns out that the warrant was invalid, and that this mass installation and monitoring was effectively an unlawful search.
"It follows that the resulting search was conducted as though there were no warrant at all," Judge Young said in his ruling [PDF].
