Carnivore

The FBI bit off some controversy in 2000 when it acknowledged it was using a custom packet sniffer called Carnivore to effect court-authorized surveillance of internet traffic.

Some network operators were uncomfortable with g-men barging in their colo to hang a black box off their network, while civil libertarians chaffed at the bureau's legally adventuresome use of some of Carnivore's features with perfunctory court notice instead of a  full-blown wiretap order.

The feds responded by giving the tool a less-ominous moniker, DCS-1000, and getting the law changed. They later put the tool out to pasture in  favor of commercial solutions.