An intrusion detection system monitors and analyzes all the incoming packets, on a given network, to detect any corresponding vulnerabilities and intrusions. It consists of four major modules: packet capturing, packet decoding, packet preprocessing and string/pattern matching. Among these, the string matching is computationally the most intensive part and a number of hardware architectures/designs have already been proposed to accelerate its performance. Consequently, an exploration of existing hardware architectures for string matching algorithms is critical. This paper identifies the most frequently used string matching algorithms and techniques, utilized for the hardware implementation. Subsequently, an exploration of various hardware architectures is provided for the identified algorithms and techniques. Finally, the implementation details of explored architectures are discussed in terms of the used device, consumed hardware resources, operational clock frequency and throughput.