I have had to block a friends e-mails from my computer. He uses a Mac computer and I have been getting several e-mails a day on my Windows vista computer witch appear to come from his e-mail address which only contain a link and when I clicked on one , Avast blocked it with a warning message that it was a dangerous url. My friend says that Mac computers cannot get viruses and will not run any security applications. Is there anything that I should do to protect my self apart from blocking him ?