Website Hacked again

I am using Sydney Pro and the website seems to be getting hacked by the same piece of code, I have removed all plugins, files and malicious script and started again. The only one constant at the moment is the theme. The malicious script keeps redirecting my buttons to Do you have any advice on how to proceed I am running security plugins but the security company suggests that it might have a back door - so I am asking every company that I use if they are aware of anything.

Hello there,

I am sorry I don’t have any company to recommend as I usually manage it myself. I’d suggest you read this codex which explains comprehensively to secure your WP site.