Mirror's Edge Catalyst

You need a combined total of 15 and since there are only 12 (hackable) Billboards in the game, you will need to complete a minimum of 3 Interventions. Hackables Billboards are denoted by yellow stairs/thunderbolts on the map and an Intervention is a random event where an NPC gets harassed by KrugerSec guards. Defeat the guards then remain close to the NPC to receive an onscreen notification indicating the Intervention is complete.