Security of External Link Redirect

If you enable the function Redirect ALL External URLs Posted in Private Forums you have a redirect function that can handle the external link to hide the source page.
But what if someone steal your redirect page to use in other website or spam emails?

Everyone can use, for example, the link

Code:

your-forums/redirect-to/?redirect=http://google.com

(for example

Code:

vbseo.com/redirect-to/?redirect=http://google.com

) to spam or to use it to "hide referrer page" (very used in illegals forums).

Is there a way to protect this function from external sites? Something like if location.host !=(mysite.com) do nothing!

All this does is strip the http referrer. Anyone smart enough to 'hack' something is more than capable of writing this line of code. I really wouldn't worry about it.