Systems and methods for classifying content as adult content and, if desired, blocking content so classified from presentation to a user are provided. Received content is analyzed using a sequential series of classification techniques, each successive technique being implemented only if the previous technique did not result in classification of the content as adult content. In this way, adult content may be identified across a variety of different media types (e.g., text, images, video, etc.) and yet processing power may be reserved if one or more techniques requiring less power is sufficient to determine that the received content is, in fact, adult content. Content classification may be performed in-band (that is, in substantially real-time such that content may be identified and/or blocked at the time results of a user query are returned) or out-of-band (that is, prospectively as new content is received but not in association with a user query).