DedSec is a huge secret collective of hackers who operate across the United States. They are first seen in Chicago during the events of Watch Dogs, indirectly aiding Aiden Pearce. While they are not directly affiliated with Aiden Pearce, their purposes often align with one another, placing DedSec firmly in Aiden's camp more often than not through Aiden's dealings with their members. Like Aiden Pearce, DedSec is against the implementation, expansion, and usage of ctOS, pointing out that it is riddled with security flaws and has been created for dubious reasons.
Part of DedSec's activities is a focus on proving that the ctOS suite of systems is both incredibly flawed and hugely unneeded. They do this by publicly hacking systems and websites hosted or used by the ctOS systems and the partners that implemented it. Famously, they hacked the ctOS official website at http://www.chicago-ctos.com, and replaced it with a totally black page featuring a prominent DedSec logo formed from ASCII characters. Mirroring this, they often tag advertisements, billboards, signposts, railway tunnels, and other landmarks with DedSec insignia.
DedSec is primarily a loose collective of hackers. Despite this, there is a sort of "hierarchy" within the organization. The organization is led by a "Council of Daves", as stated in an audio log by DedSec member G1gg1L3s in an audiolog. They are known by this moniker because of their use of "Dave" in online handles. This council likely oversees the militant arm of DedSec, which is first discussed when Clara explains the increased security presence at a ctOS center as being the result of a "failed attack".
Before the events of Watch Dogs, a corporation by the name of Umeni hired a group of engineers to create a system. When the system failed, liability was placed on the engineers, and not the corporation, resulting in the engineers being jailed for crimes they did not commit. After exiting the prison system, these engineers, angry with Umeni and seeing the rising power of Blume, formed the DedSec organization and established the headquarters seen in the Watch Dogs: Bad Blood DLC.
During the events of Watch Dogs, the Chicago arm of DedSec watches Aiden Pearce with great interest, seeing his attempts to bring down Blume as aligning with their own. Accordingly, several members begin to contact Aiden, giving him the information and means to target former and current Umeni executives. While this is part of their revenge scheme, it is also part of their greater goal to take down Blume, who relies on a lot of Umeni technology and contacts. They later send Aiden into Danny SoSueMe's mansion in order to recover data that had been stolen from them, and later, in reward, tip him off as to a shipment containing a Biometric Assault Rifle and the locations of two high-rank Chicago South Club members.
DedSec, until this point in the game, were merely passive hackers, hackers of opportunity. With the inclusion of Aiden's skillset, however, and the death of Clara Lille, whom they proclaimed a martyr, DedSec became even more militant than before. They contact Aiden as he is hacking a ctOS satellite, and request time to search the system and collect data for their revenge, which Aiden refuses. DedSec tells him that they won't forget about this, and after the events of Watch Dogs, proclaim that their reputation has been damaged, and they declare war on hackers such as Defalt, as well as Blume and the citizens of Chicago at large.
Watch Dogs: Bad Blood
While investigating the "Council of Daves", it's shown that the rest of DedSec's leadership is tired of the social media posturing and showmanship of the other Dave's, and that this faction desires "real change" through militarization. As part of a plan to achieve this, a rogue Dave lured Dave04 and DaveZB to the Ambrose Theater, murdering them. The rogue Dave video taped Defalt meeting with the Daves, encoding the video using QR onto Pawnee Dam, and notified the Daves of the murder, implication Defalt as the murder in the hopes of starting a full on war. To further this, he arranged for Daveftp, Dave Capisano, and Dave_of_Spades to be ambushed during a fake meeting at a Pawnee construction site by Fixers, but the Daves were protected by Raymond Kenney, who had learned of the plot just in time to save them. Kenney told the Daves they were now indebted to him.
After the public take down of ctOS and Blume, DedSec exploded after the events of Watch Dogs. In their San Francisco branch, DedSec boasts at least one million followers and subscribers, many of which are active hackers or protestors. They fight against the SF ctOS system, and use the same tactics as DedSec in Chicago, namely hacking and art protest. The protagonist of Watch Dogs 2, Marcus Holloway, joined DedSec after being accused of a crime he did not commit, mirroring the creation of DedSec. In Watch Dogs 2, you will be asked to build DedSec to even greater heights, grabbing more resources, man power, and pull in San Francisco.
Council of Daves