In 2015, the FBI hacked Tor to identify users of child sex websites. But despite requests being made in court, it's now refusing to reveal the finer points of how it carried out the operation. The original hack saw the FBI seize servers running a paedophile website called Playpen. But rather than shutting it down, the agents continued to run the servers, using software to identify the real IP and MAC addresses of users, despite the fact they were using Tor to access the site. ISPs were forced to hand over customer details and arrests followed.
The FBI refers to the approach it used as a network investigative technique. But despite being asked to reveal the code it used by the trial's judge, reports The Register, the FBI is claiming that such information is not relevant to the case. From FBI special agent Daniel Alfin in the court filings:
The exploit merely enabled the government to bypass the security protections on Michaud's computer to deliver the NIT instructions. Knowing how someone unlocked the front door provides no information about what a person did after entering a house.
The FBI has explained how parts of its code works, but it's unwilling to reveal how it managed to acquire IP addresses and track users across Tor's obfuscation. It's understandable: If it does explain how it worked, others will be able to work around it in the future. It's now submitted a private note to the judge to explain exactly why it's unwilling to give up the information.
The FBI's presumably also unlikely to spill the beans on the hacking of the San Bernardino iPhone. Whether it chooses to share that information with Apple, at least, still remains to be seen.
Illustration by Tara Jacoby; source image via Shutterstock