You may soon be able stop your packet sniffing, WEP cracking neighbors from stealing your precious internet with Wi-Fi blocking paint. Researchers from the University of Tokyo have developed an aluminum-iron oxide that resonates around the frequencies used by Wi-Fi. This means that it will absorb electromagnetic waves in that frequency.
So you ask, “why hasn’t this been developed already?” Well, until now most wave absorbing materials have only been able to block frequencies up to 50Ghz, while modern wireless communication uses frequencies above 100GHz. The structure of this new material distorts the bonds between oxygen and iron, allowing for absorption for frequencies up to four times higher than before.
Sounds like some fantastic stuff. So save the trouble of turning your house into a bunker equipped with Faraday cages and just paint your walls with a fresh coat of paint.