Significance Optical fiber sensors play an increasingly important role in safety monitoring areas in the smart Internet of Things (IoT). Particularly, a fiber-optic distributed acoustic sensor (fiber-optic DAS) based on the phase-sensitive optical time-domain reflectometry (Phi-OTDR) technology provides a highly dense, cost-effective, and continuous environment measurement way over a wide range. All kinds of vibration sources can be sensed and located with high sensitivity and precision utilizing the widely laid ordinary telecommunication cables, and thus fiber-optic DAS has been applied in various ground listening applications, such as natural disaster prediction of ocean-floor seismic activity, volcanic events, and earthquake, energy exploration in oil and gas industry, and civil infrastructure monitoring in the pipelines, railways, and perimeters. It leads to a new generation of large-scale fiber-optic IoT for ground and underwater listening technology. From the current research status in China and abroad, DAS is becoming mature in its hardware performance, such as the demodulation fidelity, sensing distance, detection bandwidth, and sensitivity, which are all approaching their perfection. However, with the rapid advance of DAS applications, the complicated and ever-changing environments for large-scale monitoring have brought about challenges of high false alarm rates due to its advantages of high sensitivity. It is difficult to achieve high-precision detection, recognition, and positioning of perceived vibration and acoustic targets, which has become the biggest technical bottleneck restricting the large-scale application of DAS technology. In recent years, driven by the development of advanced signal processing and artificial intelligence (AI) technology, the signal processing methods of fully intelligent DAS with high accuracy and real-time performance in practical complex environments have become a research hotspot and focus in the field of fiber-optic sensing. The signal processing method in DAS plays a crucial and decisive role in improving the intelligent perception ability of the entire system.