Actually, it's trivial to hack into a wireless router with MAC address
filtering enabled. Just sniff the traffic to/from that wireless
router and collect the MAC addresses being used. The MAC
addresses are NOT encrypted. Then, just change the MAC address of
of your computer to one of them, and you're on.

http://www.irongeek.com/i.php?page=security/changemac

That's assuming there's no data encryption. I use both encryption and MAC
filtering.

Nevertheless, I appreciate this information, as the book I read indicated that
you needed hardware to spoof a MAC address. (Perhaps the author was talking
about what was required to sniff it.)

A friend of mine remarked that both he and I were relatively safe from such
attacks. "Why would anyone be interested in accessing //our// computers?"
Indeed. This is true for most users. Of course, it's no excuse for not taking
simple steps to protect yourself.