Hyperlink feature of editor being used to spam

[Snowhog]

Running vBulletin 4.2.3 Patch Level 2

The Basic and Enhanced Editor (we have the Enhanced Editor as the default when a user registers) has a Hyperlink button. We have been experiencing a number of (maybe the same person using different usernames) new registrations where the first post is responding to an existing post and 'almost' makes sense given the prior posts contents, but they always contain a hyperlink (the text varies) pointing to the same services website.

If I remember correctly, changing the default editor under User Registration Options > Default Registration Options > Options > Message Editor Interface to Do Not Show Editor Toolbar is the only way to prevent this from happening without the new member going into Settings > General Settings and changing the editor to either Standard or Enhanced.

Is there any way to make the Standard and Enhanced editor available as a function of Usergroups Promotion, forcing new registrations to use of the Basic editor only?