One KEY thing to keep in mind BEFORE a hack:
Always have a backup.
BackWPup is a great (free) plugin that’s super-easy to use and setup automatic backups to Dropbox and other Cloud storage services. I use it on all my sites and highly recommend it (Multi-site compatible as well).
The following was originally posted by a Volunteer moderator on the WordPress.org forums, but they are great links worth keeping a copy of for later reference:
You need to start working your way through these resources:
- http://codex.wordpress.org/FAQ_My_site_was_hacked
- http://wordpress.org/support/topic/268083#post-1065779
- http://smackdown.blogsblogsblogs.com/2008/06/24/how-to-completely-clean-your-hacked-wordpress-installation/
- http://ottopress.com/2009/hacked-wordpress-backdoors/
Additional Resources: