The Federal Bureau of Investigation (FBI) is a federal law enforcement agency that appears in Watch Dogs 2. They have their own division and office in San Francisco and are working with Blume. They are featured within the storyline as an opposing faction against DedSec.
Throughout the course of Watch Dogs 2's story, the FBI covertly spy on DedSec (which DedSec only discovers thanks to Miranda Comay's connections), cooperate with Dusan Nemec, and illegally detain Wrench and take his mask from him as a means of psychological torture. Their end goal in targeting not only DedSec, but all hacker groups, is to maintain control over as many zero days as possible without any competition. Marcus sneaks into the FBI's Bay Area headquarters in Dellums Towers, in Oakland, to place a transceiver on the building's roof, in the mission W4TCHED.
The FBI also appears in online side missions. One of them involves stopping two FBI Agents from revealing compromising info on DedSec. Another online side mission involves hacking the FBI Agents to get info on them.