High speed security log analytics using hybrid outlier detection The rapid development and integration of Information Technologies over the last decades influenced all areas of our life including the business world. Yet not only the modern enterprises become digitalised but also security and criminal threats move into the digital sphere. To withstand these threats modern companies must be aware of all activities within their computer networks. The keystone for such continuous security monitoring is a Security Information and Event Management (SIEM) system that collects and processes all security related log messages from the entire enterprise network. However digital transformations and technologies such as network virtualisation and widespread usage of mobile communications lead to a constantly increasing number of monitored devices and systems. As a result the amount of data that has to be processed by a SIEM system is increasing rapidly. Besides that in depth security analysis of the captured data requires the application of rather sophisticated outlier detection algorithms that have a high computational complexity. ...