To unlock this, you must use Sabotage BEFORE your opponent uses an ability. When done, it makes a sound effect and the opponent will kinda glitch a little in appearance. You can do this in Wolfpack mode or Public Matches. I did this in Wolfpack on Prison, viable enemies to try it on are during Defense, during Infection, or on the later groups of enemies that are colored red. For the red enemies, I would wait until they noticed me then use Sabotage, then they usually try an ability and it works.
EDIT: Alright, so there's a bit of confusion regarding this. Sabotage is unlocked at level 28. It is actually a ranged weapon, not an ability. Hopefully this clears up some confusion.