Well shit. I didn't even realize he could slip the ball around.
Tried to do a few online hacks, and only one was completely successful, and that was because the guy was swimming and I ended up getting stuck in some rocks along the shore. Another person tried hacking me while I was in the area, and I ended up finding them around 80% and killed them. A couple of hack attempts I got caught, but escaped. One of them went to a roof. Then a couple of people managed to hack me as I couldn't find them. One of them taunted me by stopping the trains constantly.
I assume the yellow circle is where the person actually is, but for the life of me I couldn't find them despite how small the circle got. I want to see if you need to be relatively close to initiate the backdoor, or if you can hack them, go a bit away, then initiate it, because I've been hacking people and initiating them almost immediately.