Wireless communication is vulnerable to eavesdropping attack due to the broadcast nature of radio propagation. In recent years, physical-layer security is emerging as a promising paradigm to prevent an eavesdropper from interception. In this paper, we consider a wireless network consisting of one source, one destination and one eavesdropper, and exploit multiple antennas at all the network nodes to improve wireless security against eavesdropping attack. Considering multiple transmit antennas at

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... source node, we propose the optimal antenna selection (OAS) scheme to enhance the physical-layer security. We also examine the conventional single-input single-output (SISO) and spacetime-coded transmission (STT) for the comparison purpose. We analyze the intercept probability performance of SISO, STT and OAS schemes in Rayleigh fading channels and theoretically prove that the proposed OAS scheme strictly outperforms conventional STT scheme in terms of the intercept probability. In addition, numerical results illustrate that with an increasing number of antennas at source and destination, the intercept probabilities of both OAS and STT schemes significantly decrease, implying the advantage of exploiting multiple antennas for wireless security against eavesdropping attack. Index Terms-Eavesdropping attack, multiple antennas, physical-layer security, optimal antenna selection, space-time code, intercept probability.