12. The one or more non-transitory computer-readable media of claim 8 , wherein determining whether the request is valid includes evaluating a referrer string.
8. One or more non-transitory computer-readable media storing computer-executable instructions that, when executed by one or more computers, cause the one or more computers to: receive a request for a font file; determine whether the request is valid; in response to determining that the request is valid, embed a first watermark in the font file at least by inserting one or more zero-length vectors at one or more locations in the font file; and serve the font file.