The community is moving towards the cloud, and its security is important. An old vulnerability known by the attacker can be easily exploited. Security issues and intruders can be identified by the IDS (intrusion detection systems). Some of the solutions consist of network firewall, anti-malware. Malicious entities and fake traffic are detected through packet sniffing. This chapter surveys different approaches for IDS, compares them, and presents a comparative analysis based on their merits and demerits. The authors aim to present an exhaustive survey of current trends in IDS research along with some future challenges that are likely to be explored. They also discuss the implementation details of IDS with parameters used to evaluate their performance.