Is a free WordPress template really free? If you go the free route, you have to be extra careful when downloading them, because some are known to harbor malicious code. The best way to test a WordPress theme is to download it to your PC, then run a test on your desktop. Using XAMPP, the free and open source package, allows you to install a Web server on your PC, then using the TAC (Theme Authenticity Checker) plugin, among a few other tools, you can scan all your theme files for potentially malicious or unwanted code.
(See the full blog post here.)