I thought about this security thing and emailed a guy that wrote Qcharts about it at one point. He recommended unbundling the brokerage from the software. I guess he was suggesting that a programmer could easily write a back door in some trading software to check your account and steal your intellectual property. Programmers do those very things, a couple guys were found to have put back doors in banking software, well documented case actually.
I have spoken to various people in my near-field and they immediately jump to the "paranoiac" thing, I'm being logical and assuming that somebody will try to steal my intellectual property just to be on the cautious side. I did work up a great system for complete security but I'm not sharing it here and I don't have it yet, it is costly to implement. I have shared the idea with a friend that is very computer savvy and he was surprised at the simplicity and effectiveness, I might lease them later on....
I would recommend a completely separate computer for trading, I have one for surfing, not worried about the security much at all, and one for trading. People have reported here that if they have one computer for trading that they can run it for years with no firewall or antivirus and never have a problem.
I would recommend a hardware firewall for the trading computer, configure it so it allows only the url's necessary for trading in or out, then add zone alarm or something that recognizes when software is phoning home and block it if you think you can run your trading without it calling in. On the cheap and simple, that is going to be pretty effective.
If your trading software can access your brokerage account then you have to not let it phone home essentially. You are stuck with the fact that somebody in your brokerage can access your computer and download your intellectual property a few bytes at a time over a long period and there is little you can do about it IMO but the hacker would have to be inside the brokerage, and using their computers and network to do that, seems a bit dicey for said hacker and hopefully a savvy brokerage would be on the lookout for such activity because were it discovered by clients it would cost the brokerage hugely in terms of trust and image.
I would not make the decision based on "Canadians are ethical", I'm laughing pretty good at that one.......