We have seen numerous waves of spam on this site. At first we setup mollom, in 2011 but sometimes it is not enough.
The very first step is to identify the user account and disable it (not delete it, we need it to find the content to remove).
Views Bulk Operations views used for despamming:
Note that this will flood your screen with
drupal_set_message for every page that is deleted, which may make the site difficult to use for a while. To top that, the final page will list the name of every page that was removed, just to make sure you had enough spam for the day.
You can also use the regular comment view to delete content and report it to mollom if you are patient enough.
You can also delete the account if you are motivated and want to grind that specific axe. Look at the regular user listing for the latest user accounts created.