Abstract: Network Intrusion Detection System (NIDS) is an intrusion detection system that attempts to discover unauthorized access to a computer network by analyzing traffic on the network for signs of malicious activity. In traditional data centers, where system administrators have full control over the host machines, vulnerabilities can be detected and informed by the system administrator in a centralized manner. But in case of cloud data centers, where the cloud users are having the independence to install and control the desired software, they can install vulnerable software’s on their managed VM’s and contravene the Service Level Agreement (SLA) and as a result loophole in cloud security are created.

Keywords: NIDS, signs, vulnerabilities, cloud data centers, Service Level Agreement.