This link does not guarantee that it will not happen. Almost on a regular basis SEC/CFTC bring people to court for things they are supposed not to do. But the fact they do, proofs that not everything can be put under paranoia. Not everybody follows the rules all the time.
Till a few years ago everybody was sure email was safe. Till the NSA got exposed.
You should read this:
https://en.wikipedia.org/wiki/Naivety
I remember vaguely that many years ago a famous company (forgot the name) in the US manipulated their software that was used for quoting prices for some future energy contracts. A client found it out by accident. Each time when he hovered with his cursor over the buy or sell price, the price changed and became more expensive; the buy went up and the sell went down. When the cursor was not on the buy or sell, the correct market prices were quoted. It was filmed and shown on internet.
Brokers should follow the rules?These people didn't.
Read this one:
https://en.wikipedia.org/wiki/MF_Global
or this one:
https://en.wikipedia.org/wiki/Refco