12. A system, comprising: a data processing apparatus; and instructions stored in a non-transitory computer readable storage system accessible by the data processing apparatus and executable by the data processing apparatus that upon such execution cause the data processing apparatus to perform operations comprising: receiving a query from a user device, the query being one or more query terms; identifying content items that are responsive to the query as unfiltered content items; determining that the query includes a filtering term, the determining comprising: comparing the query terms to a list of filtering terms; and determining, in response to a match of one or more of the query terms to at least one of the filtering terms, that the query includes a filtering term; and in response to the determination that the query includes the filtering term: identifying filtered content items based on the query and the filtering term; providing search results for the filtered content items to the user device, each search result referencing a filtered content item; providing the user device access to a verification service that provides access approval or access denial for search results for the unfiltered content items that are responsive to the query, determining whether access approval or access denial is received from the verification service in response to user identification data provided to the verification service; if access approval is received from the verification service, then providing search results for the unfiltered content items to the user device; and if access denial is received from the verification service, then precluding the provisioning of search results for the unfiltered content items to the user device.
12. A system, comprising: a data processing apparatus; and instructions stored in a non-transitory computer readable storage system accessible by the data processing apparatus and executable by the data processing apparatus that upon such execution cause the data processing apparatus to perform operations comprising: receiving a query from a user device, the query being one or more query terms; identifying content items that are responsive to the query as unfiltered content items; determining that the query includes a filtering term, the determining comprising: comparing the query terms to a list of filtering terms; and determining, in response to a match of one or more of the query terms to at least one of the filtering terms, that the query includes a filtering term; and in response to the determination that the query includes the filtering term: identifying filtered content items based on the query and the filtering term; providing search results for the filtered content items to the user device, each search result referencing a filtered content item; providing the user device access to a verification service that provides access approval or access denial for search results for the unfiltered content items that are responsive to the query, determining whether access approval or access denial is received from the verification service in response to user identification data provided to the verification service; if access approval is received from the verification service, then providing search results for the unfiltered content items to the user device; and if access denial is received from the verification service, then precluding the provisioning of search results for the unfiltered content items to the user device. 19. The system of claim 12 , wherein identifying filtered content items based on the query and the filtering term comprises: initiating a search of an information corpus for content items that are responsive to the query; identifying the content items that are responsive to the query as the unfiltered content items; filtering the content items that are responsive to the query by the filtering term to exclude some of the content items that are responsive to the query; and identifying the non-excluded content items as the filtered content items.