If you haven't already you should open a ticket immediately. While a few dreamhost employees do read this forum, it's not an official method to contact support.
Dreamhost has tools that can help clean up after a hack, but that cleanup may not be perfect. Hopefully you have a backup of your site in case it's needed. Also it's your responsibility to secure/harden your sites against hacks. Most hackers sneak in thru leaks in themes and plugins, not wordpress core itself.
Some dreamhost wiki articles:
My Wordpress site was hacked