Have you seen the previews for the new movie, Pulse? Apparently, the plot is that wireless technologies make a connection to a world beyond our own, and now creatures from another dimension are coming through our email to kill us.
First off, most big companies are using Barracuda spam filters now, so nothing except only the choicest e-mails are making the circuit. Your Yahoo! account will probably still get a bunch of daemons, but that's life. Consider it "Survival of the Smartest."
Secondly, these creatures would never be able to come through the Internet. The people who made this movie just don't understand: the Internet is not a dump truck. You can't just put stuff on it and dump it off somewhere else, for creatures to thrive in. The Internet is a series of tubes.
And even if these demons could fit through the tubes, there's enormous amounts of material, enormous amounts of material in the tubes already, so if someone did send you an infected email, it might take 5 days to get to you. Unless these are some really potent demons, they're not going to last 5 days without water.
And of course, there's always 128-bit WEP encryption, or you could just not broadcast your SSID out to the world. Or get eaten by undead demons coming through your wireless network, see what I care.
Thus the premise of "Pulse" is ridiculous, unless of course Senator Ted Stevens (R-Alaska) is able to squash any Net Neutrality amendments to any upcoming Senate bills.