From the yesteryears i remember that Windows can be hijacked and is virus prone and now a days even Apple removed a line that "Mac is not virus prone" as was attacked by a trojan. The latest in the trend is Android Application Stack which is now proved to be hijacked....checkout this link:
Researchers create "clickjack rootkit" for Android that hijacks apps
Researchers create "clickjack rootkit" for Android that hijacks apps
