Thank you very much for taking a look into this.
More information I can give:
For I can see on the scans I did the file in question is "returnyGx.php" a "Backdoor:PHP/Shell.N".
Immediately after upload of this file through a ftp client my account was suspended.
My account was suspended yesterday due to host of malicious files.
This happened when I was going to upload an add-on and it just cut me out of the ftp. I automatically realised it was malicous.
I've had my account for a long time and made serveral changes to my website before and I never had...