A method and apparatus in a data processing system for detecting monitoring of access to content. Content from a source using an identifier is requested, and a set of identifiers used to reach the content is sent to a validation service. The validation service retrieves content using the set of identifiers. Identifiers within the retrieved content is compared with identifiers located within the set of identifiers. If a match between identifiers in the set of identifiers and those identifiers in the retrieved content is absent, a response is generated indicating that access to the content is being monitored. In response to receiving the response from the validation service, the receipt of content from the source is selectively prevented.