We could add a new setting
If this is enabled, piwik.php will check the incoming Page URLs against the list of URLs recorded for this website id.
Also, the http referer should be checked and it should be non empty, and have one of the known domain URL.
This new feature would help prevent fake requests to a Piwik server.
In the cases where the Referer header is suppressed, the check may have to allow an empty referrer.
I think we'll have to ignore the visits without referer or it would make the new feature incomplete (ie. you would just have to generate a proper URL and empty referer to record unwanted visits)
As I recall, the rationale for this feature was where UnrelatedSiteB copy & pasted content from SiteA. In this use case (copyvio), wouldn't we want to report the suspicious tracking (as opposed to ignoring it)?
This is for this use case as well as intentional requests. I don't think we want to report, or we could, but this would be in a V2.