There are tools made to help spot hidden fraud like impression stacking, where fake impressions are added under your ad without your knowledge. Trackers like Voluum, RedTrack, or Binom can show strange patterns, such as too many impressions with no clicks. Some networks also offer their own fraud detection. You can also use fraud-check tools that scan placements and IPs for suspicious behavior. Watching your stats daily can also help you notice things that don’t look right. What tools or signs have you used to check for fake activity in your campaigns?