Classifying users of a database

A computer-based system and method for classifying users of a database including obtaining an activity rate time series describing activity level of a database user versus time, extracting features from the activity rate time series, the features including a measure of repetition in the activity level, mean activity load and a percentage of the time in which the user is active, and determining a type of the database user based on the extracted at least one feature. The measure of repetition in the user activity is calculated by performing a Fourier transform on the activity rate time series to produce a transformed series; detecting spikes in the transformed series; and measuring a percentage of information in the transformed series which is included in the spikes.