With the introduction of the Internet of things (IoT), the number of wireless devices and volume of wireless data traffic has skyrocketed. The system proposed in this paper focuses on Internet of things (IoT) performance and security analysis based on Wi-Fi systems. In order to perform this analysis, an IoT wireless temperature and humidity sensor will be developed; whereby, the microcontroller will communicate and send collected data to an IoT cloud platform where the collected data can be analyzed and stored. An android application is developed from scratch to fetch the data from the IoT cloud platform, display the data in the application and send messages to the cloud. The sensor, microcontroller and the android application will communicate wirelessly with each other through Wi-Fi and MQTT (MQ Telemetry Transport) protocol. The performance and security of the whole system will be tested and analyzed; and ways to improve both the performance and security of the IoT system is presented. The system is subjected to Distributed Denial-of-Service (DDoS) attack, with Security Information and Event management (SIEM) is implemented for detection and DDoS attack prevention.