I've hacked other players maybe 5 times or so, and I've only been discovered once. It was my own stupidity. I didn't realize I had so much time to start the download and ended up doing it in plain view. He found me almost immediately and mowed me down. I've had good luck staying in cars and either parking and hiding or just doing circles if I've got enough room to do it inconspicuously. The handful of times I've been hacked have been hit or miss. The first two times I failed because I didn't really know what I was looking for. Once I got the hang of it, I found the next two people.