I installed a windows 7 on the parallels desktop 9 on my mac mini with Mac os Mavericks. As I understand that there are some shared folders between Mac os x and Windows 7 virtual machine. I've been wondering whether it's safe to use Windows 7 to surf the net without anti-virus program. If the Windows 7 VM gets affected by virus, can these malware or virus affect the Mac os x host? I mean, there are any so-called cross platform virus I should pay attention to.
Ok, so why would you "surf the net" from a Windows VM instead of Safari? Unless it's to access a site that is not Mac-friendly, that just doesn't make sense. While the potential for damage to the Mac side is not high, it's certainly not impossible. Windows is Windows - you need to run something. Check out Microsoft Security Essentials. It's free and supposedly very good.
