If you visit Asus' website, they have a
download section that allows you to download the latest BIOS (Appears to be rev 1016, 1805 for beta) and the Asus Update utility, which is a BIOS update utility that can be run from inside windows. I did all of my BIOS updates with that utility and never had any problems with it, so I'd say it's a safe bet.
Good luck actually getting the file though, Asus' servers suck. You might have the best luck clicking on the Global link for downloads as opposed to the USA link (unsure of the other servers, been a while since I've downloaded anything from Asus).