Operation Pacifier. The FBI raided a TOR server that was hosting child porn and installed some flash files embedded in every page that dialed home outside of TOR, using a broken version of flash that just happened to be installed in the official TOR Browser Bundle. But they couldn't shut the site down because if they did, they wouldn't have any evidence of people accessing the porn. So for a few weeks the FBI literally ran a Child Porn ring, complete with photos and video downloads.
This Op Pacifier is also notable because they got a Part Time Traffic Court Judge to approve this warrant for "every computer user on every computer everywhere in every jurisdiction for all of time" because the District Court Judges in the same building refused to sign off on it for the FBI. Ditto the actual house raids, almost all of them were signed off on Magistrate Judges because again, the real judges smelled a rat and refused.
This apparently was upheld by SCOTUS, so now if the FBI wants to break into your computers in say, Arkansas, they can ask a Traffic Court Judge in New York City they know to sign off on it, and it's just fucking dandy.
Oh, and this being a blatant 4th Amendment violation started getting the Op Pacifier cases thrown out by some judges, so the SCOTUS changed the rules to effectively state "The 4th Amendment does not exist if you use a computer."