John Carter gets our attention with this! "There's a particularly nasty virus associated with the email that supposedly comes from UPS. The virus actually causes the mouse on a Mac to freeze up after about 15 seconds, you then have to reset the mouse, and it freezes again 15 seconds later.
"But this can only happen if you have a Windows machine on the same network as your Mac. Once the virus hits Windows, it infects all machines in the same network, including the Mac.

"The moral of the story is do not run Windows without fully protecting the Windows OS with an A/V program - like AVAST. The Windows OS also needs Malwarebytes and SpyBot Search & Destroy software installed and running all the time in addition to AVAST."