Castle is described as 'Simple developer-friendly APIs lets you send activity from web and mobile apps. Castle builds behavior models over what's normal for your site and each user account' and is an website in the Development category. There are more than 10 alternatives to Castle, not only websites but also apps for Linux, Mac, Windows and Self-Hosted solutions. The best alternative is Splunk, which is free. Other great sites and apps similar to Castle are Qualys Cloud Platform (Paid), IQLECT (Freemium), Exabeam (Paid) and Fortscale (Paid).
Splunk is software that provides unique visibility across your entire IT infrastructure from one place in real time. Only Splunk enables you to search, report, monitor and analyze streaming and historical data from any source.
Qualys, Inc., is the most widely-deployed information security and compliance cloud solution in the world with over 7,700 customers including a majority of the Forbes Global 100 and a majority of the Fortune 100.
IQLECT is the creator of Ampere, a real-time big data analytics platform. Various apps for data center infrastructure monitoring, clickstream analysis, log analysis and others can be deployed on the platform.