Operation Sundevil
The US Secret Service's nationwide sweep of the BBS underground in May 1990 — lots of seizures, very few convictions.
Between 7 and 9 May 1990, the Secret Service and the Arizona Attorney General's office served search warrants at around two dozen addresses in more than ten cities. The target was the network of BBSes where stolen credit card numbers, long-distance codes and phreaking know-how changed hands. Roughly 40 computers and tens of thousands of floppy disks were hauled away, and a press conference in Phoenix billed the whole thing as a decisive blow against computer crime. The name came from Arizona State University's teams, the Sun Devils.
The results were thinner than the press release. Few prosecutions went anywhere, and much of the seized hardware sat untouched for years. Sundevil is often lumped together with the parallel hunt for the Legion of Doom and the raid on Steve Jackson Games, though those were separate investigations. Together they had the same effect: the question of which constitutional protections applied online landed on the table for the first time, and the EFF was founded that summer.