The hacking collective DedSec was first introduced in Watch Dogs as a small anti-government group of hackers. However, Watch Dogs 2 will increase the membership of DedSec significantly and add a number of other rebellious underground organizations.
ctOS 2.0 is an extremely powerful system, and Marcus Holloway will not be able to deal with it alone. DedSec has its own application that will help recruit new members, test them and eventually integrate them into the group.
The goal of the DedSec and others alike is simple – bring freedom to all the citizens of San Francisco through mutual hacker attacks at the ctOS.