Content level filtering or masking of digital content that is broadcast, multicast, or otherwise distributed to receivers in a communications system. Instead of controlling the content only at the location of the broadcaster or at the receiver, the present invention provides the capability to control access to the content, and manipulate the content itself via a masking operation, at any point in the content distribution hierarchy or transmission chain. The present invention provides enhanced customer choice to different versions of the content and content creator control over content deemed to be too objectionable or too sensitive to be transmitted without partial concealment or obfuscation. A mask may be specified to change the content distributed further down the distribution hierarchy. The mask may be a distorted or opaque two dimensional (2D) region (for video content), or a replacement audio segment (for audio content), or a distorted or opaque three dimensional (3D) volume (for 3D content), carried separately from the original content in digital multimedia broadcast, multicast, or point-to-point distribution systems. The present invention also specifies the co-transmission to a receiver of encrypted, masked content, which may be used to "undo" a masking or obfuscation operation previously performed anywhere upstream of the receiver in the distribution channel.