Prelude is described as 'Universal Security Information & Event Management (SIEM) system. It collects, normalizes, sorts, aggregates, correlates and reports all security-related events independently of the product brand or license giving rise to such events' and is an app in the Security & Privacy category. There are four alternatives to Prelude for Linux, Mac, Self-Hosted solutions, SaaS and Windows. The best alternative is Splunk, which is free. Other great apps like Prelude are SIEMonster (Free, Open Source), AlienVault (Freemium) and DNIF (Freemium).
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.
Alienvault integrates and correlates many popular network and security monitoring tools in one suite, inlcuding OSSEC, nfdump, log analyzers, nagios, and nessus and analyzes it against its own community-driven threat feed.