Watch Dogs has several multiplayer modes, none of which are accessible from the get go. In order to start challenging other players, you’ll first need to unlock the game’s main multiplayer mode by completing the campaign mission “Hacking Contract.” Fortunately, it’s only the fifth mission in the game and won’t take you long to complete.
Once that’s done, it’ll be possible to perform an intrusion into other players’ games. Likewise, your game will be intruded upon by other players. If and when that happens, your objective will be to kill the hacker in your game.
In order to find the hacker in your world, you’ll have to profile everyone you meet with the gadgets you have at your disposal. Hackers will attempt to remain inconspicuous as they appear as NPCs in your world. Bad ones will run out of place and make their presence known to you. Hackers can hide anywhere—on rooftops, in vehicles, and behind objects.
Keep in mind that you’ll be able to profile your targets from looking at them directly, using surveillance cameras, or while driving a vehicle.
If you’re in a crowded place, you should fire your gun and watch for the public reactions. NPCs will freak out, while hackers don’t normally do.
When you intrude into another player’s match, your objective will be to hack them without getting caught. The first step is to hack them—which you can do by looking at their face. Like profiling, it’s possible to hack the enemy while driving a vehicle or through surveillance cameras.
Once you acquire your target, you’ll have one minute to get away as far as possible. When that’s done, the you can initiate the backdoor installation, at which time you’ll have to spend hiding from your opponent while remaining within the hack zone.
If you do get caught, you won’t be able to kill your target. You’ll just have to get away.
For successfully hacking a target, you’ll acquire money and experience points which you can use to level up and unlock abilities that make it easier to hack your targets.
This sums up everything you need to know about online hacking in Watch Dogs.
