Clean nulled Wordpress Themes

Hey guys, long time no see.

I recently got my hands in some very HQ wordpress theme which is nulled (I know I'm a cheapass but this is temporary). How to check if the theme has no backdoor spyware or virus. I have a Bit Defender subscription (I bought this one, because is the best out there in my opinion and is worth it)., but I can'd find any typical virus. I'm more concerned about backdoors when I host the website. Thanks in advance!!!

you nulled a theme, you could go get a cracked Acunetix and use it