Moodle keeps detailed logs of all activities that users perform on your site. You can use these logs to determine who has been active in your site, what they did, and when they did it.
Moodle has a modest log viewing system built into it. You can see the logs under Administration | Reports. These reports enable you to look at the raw logs for a course. However, for sophisticated log analysis, you need to look outside of Moodle. The following section will help you with the tools you need to view and analyze your site logs.