Cybercriminal Eric Eoin Marques pleaded guilty in an American court this week. Marques faces up to 30 years in jail for running Freedom Hosting, which temporarily existed beyond reach of the law and ended up being used to host drug markets, money-laundering operations, hacking groups, and millions of images of child abuse. Investigators were somehow able to break the layers of anonymity that Marques had constructed, leading them to locate a crucial server in France. This discovery eventually led them to Marques himself. Marques was the first in a line of famous cybercriminals to be caught despite believing that using the privacy-shielding anonymity network Tor would make them safe behind their keyboards. The case demonstrates that government agencies can trace suspects through networks that were designed to be impenetrable. Marques has blamed the American NSA's world-class hackers, but the FBI has also been building up its efforts since 2002. And, some observers say, they often withhold key details of their investigations from defendants and judges alike-secrecy that could have wide-ranging cybersecurity implications across the internet. The FBI had found a way to break Tor's anonymity protections, but the technical details of how it happened remain a mystery. Perhaps the greatest overarching question related to the investigation of this case is how the government was able to pierce Tor's veil of anonymity," Marques's defense lawyers wrote in a recent filing.