WordPress footer.php virus!

I have a virus in my footer.php and I can’t seem to find the source of it. It seems to inject hidden links to spammy websites.

I have change the permissions of my footer.php to 444 and removed the links from my footer.php but it keeps on rewriting my footer.php to have these hidden spam links.

Can anyone figure out what the source of this virus and how I can completely remove it.

Here is a sample of the code it injects below.