While this definitely should be a concern to those who really understand the power and potential of the Internet, there is one positive side-effect to so many machines hiding behind NATing routers — security. A NAT router typically acts like a packet-filtering firewall that keeps pretty much all machines behind it safe from the common automated attacks and worms. This is an accident of circumstance, but does help keep many machines from unwittingly spewing infectious trash onto the ‘net.