I run Sophos AV on my Mac and it seems to scrutinize anything that comes into the machine from the Internet. I run Windows 8 inside of a virtual machine using Parallels Desktop. Does my Mac Sophos protect downloads that come into the virirtual machine? I ask because I also run Microsoft Defender on the VM and it is something of a resource hog. It seems to me that running two antivirus programs is like wearing a belt with suspenders. Windows apps see a download coming is just as they would on a nuts and bolts machine. The communication is mediated by an OS X Parallels process that I suspect is monitored by Sophos AV. Also, I use Windows for only a couple of business applications--Quickbooks and Microsoft Streets & Trips. The only browsing I do is to Intuit forums. The only email use is sending quotes using Thunderbird for Windows. Thanks for your wisdom.