Earth 'noise' could attract alien invaders

From the New Scientist magazine, 3rd May 2008, a scientist is reported as saying that we are too late to stop an alien invasion. The article says,

No matter how quiet we try to be now it's too late to prevent alien invaders. So says Alexander Zaitsev of the Institute of Radio Engineering and Electronics in Moscow, Russia, who points the finger at astronomers.

For 40 years, astronomers have fired microwaves off objects to chart near-Earth space and track the movement of close asteroids - and these signals are traceable back to us.