Need solution for Mac running Windows Apps with Parallels

I recently added Parallels and Windows 7 to my Mac so I can run some Windows-only software.  I have one iMac desktop, and a macBook that my part-time assistant uses, and we're connected wirelessly through an Airport Extreme.  Will the Norton product I use for the Macs also detect and protect my Macas from Windows vulnerabilities?  Or, do I have to buy and install Norton for Mac protection AND Norton for Windows product(s), as well?  Thanks