The reputations of content sources are tracked as running rates of content origination. Information concerning content origination from multiple sources is received and aggregated. The aggregated information is used to calculate running rates of content origination. An initial running rate of content origination can be calculated based on the number of detections of originations from a given source over a period of time. Running rates can be updated based on additional detections from the source since the last update. As incoming electronic content is received from specific sources, the running rates from given sources are used to determine whether to block or allow the incoming content. Reputation characterization percentages can be calculated based on the running rates, and incoming content from a specific source can be blocked if a reputation characterization percentage is above a given threshold.