http://windows.microsoft.com/en-au/w...website-owners
Note the last drop-down (Can I customize a list of trusted sites for SmartScreen Filter in Internet Explorer 8? ) about Trusted Sites. I don't have Windows 8, but it sounds like you can add the fansub sites to the Trusted list, and tell Smartscreen not to automatically check them.
edit: the fix seems to be an Internet Explorer specific one. It may not work if you use something else.