This document reviews various techniques for detecting replay spoofing attacks in automatic speaker verification systems. It summarizes several existing methods that use features like spectral centroid deviation, magnitude spectral root cepstral coefficients, phase spectral root cepstral coefficients, instantaneous frequency cosine coefficients, and convolutional neural networks. The best performing approaches achieved equal error rates of around 3-7% on evaluation datasets, representing a relative improvement of 60-72% over baseline constant Q cepstral coefficient systems. Deep learning methods using residual neural networks and spectrogram inputs were also found to provide good detection performance. The paper concludes replay spoofing remains a significant threat and efficient feature extraction and classification methods are needed to effectively counter such attacks.