Virus Dropping Script in files?

HI Everyone,

So basically i keep getting errors, like parse errors and such.

WP shows me exactly where the issue is and when I FTP the specific file, open it up and check the coding – theresa whole lot of crapp-ass coding at the bottom which I have to delete.

once deleted it solves the problem.

The issue is that it keeps coming back after a few hours or days – and I have to repeat the process of finding the file and deleting the script that pops up.

How do I get rid of this permanently?

Many thanks!

Lall