Sorry --- but each platform is vulnerable, regardless of OS deployed, and bad actors in fact - do compromise all platforms. Ironically OSx Yosemite and iOS are among the most easy to use consumer grade products but almost exclusively rely on code signing and a few other weak security measures which can be easily bypassed by bad actors with weak technical skill. App vetting is also the other measure most Apple products tout, but there are easy work arounds there as well. As Apple gains greater presence, those products will be more targetted by nation states and bad actors (criminals).
To take this conversation further would be to take it places that it should not go as we all are just trying to help the OP recover his system and fix the vulnerabilities and mitigate risk going forward.
Unless you have a need to know, and work within the penn testing / forensics / malware analysis / Incident response side of the cyber security industry, you likely will not have the level of knowledge -nor the understanding on the nature of this threat. And that's OK ---- we all are just trying to help the OP recover his system and avoid these types of compromises going forward.
I stand by the recommendations to the OP --- it is his choice how to proceed.