22. A system that implements a cloud service for providing optimized web domains classification based on progressive crawling with clustering, comprising: a processor configured to: distribute a first Uniform Resource Locator (URL) content categorization data feed to a first plurality of subscribers, wherein the first URL content categorization data feed is collected using an optimized web domains classification based on progressive crawling with clustering to determine which category clusters to publish for each categorized web domain, and wherein the distributing of the first Uniform Resource Locator (URL) content categorization data feed to the first plurality of subscribers comprises: receive a request to classify content for a first web domain from a first security device; automatically classify the content for the first web domain, comprising: crawl a plurality of pages in the first web domain; determine a category for the plurality of pages in the first web domain; group more than one page having the same category into a first cluster; determine whether a number of the more than one page of the first cluster exceeds a first threshold; and in the event that the number of the more than one page of the first cluster does not exceed the first threshold, select a new page within the domain to crawl and classify; and send the classification for the content for the first web domain to the first security device; and distribute a second URL content categorization data feed to a second plurality of subscribers, wherein the second URL content categorization data feed is collected using an optimized web domains classification based on progressive crawling with clustering to determine which category clusters to publish for each categorized web domain; and a memory coupled to the processor and configured to provide the processor with instructions.
24. The system recited in claim 22 , wherein the processor is further configured to: receive a request to classify content for a second web domain from a second security device; automatically classify the content for the second web domain; and send the classification for the content for the second web domain to the second security device.