In this paper, we focus on securing communication over wireless data networks from malicious eavesdroppers by using smart antennas. While conventional cryptography-based approaches focus on hiding the meaning of the information being communicated from the eavesdropper, we consider a complimentary class of strategies that limit knowledge of the existence of the information from the eavesdropper. We profile the performance achievable with simple beamforming strategies using a newly defined metric called exposure region. We then present three strategies within the context of an approach called Aegis, which uses virtual arrays of physical arrays to significantly improve the exposure region performance of a wireless LAN environment. Using simulations, analysis, and field trials, we validate and evaluate the proposed strategies.