PHP injections on my WP installation – how do I get rid of it ?

Hi everybody,

I have some severe problems with php injections on a few of my WP installations and want to get rid of that.

In every php file I have a header looking like this:

[ Please do not post malware scripts like that here. ]

I don’t have any plugins I don’t use, I only have one theme per installation installed and I always upgrade my WPs. I also use the plugin “Bulletproof Security”.

My two questions: How does that code come into my PHP files and how can I get rid of it…?

Thanks in advance for your help!!
*cheers, Danny