It might be a hack, or it just might be a conflict with a plugin or theme.. etc.. hard to say without investigating.
As for a backup, yup, you can do it yourself. You can also check with your host, they might have a 24 hour backup service.
The easiest way is to do a backup locally, grab and pull all the files down. nice and easy. You won’t be able to take advantage of most of the plugins out there, right now, being your website is down.
here are a few tips to get you going again:
1 – Try disabling /wp-plugins (you can do this by renaming)
2 – Try disabling /wp-themes (same as above)
3 – Manually replace core (yes, download it locally and replace wp-admin and wp-includes)
Now mind you, you might be suffering from the recent outbreak: https://blog.sucuri.net/2014/07/mailpoet-vulnerability-exploited-in-the-wild-breaking-thousands-of-wordpress-sites.html
If so, the process might be a bit more exhausting being that all your PHP files are likely messed up.
Thanks
