Automatic assignment of user group

[fgenetics]

Is there a modification available where a user registers and he can be placed in an usergroup other than the "registered users" user group?

The problem I am facing is as follows.

We currently have 10,500 members, registered.
We want to make certain sections of the board NOT available to new members - NOT VISIBLE.

So I was wondering if they could directly go into another usergroup, and this usergroup have only limited access.
They can be promoted to registered members at a later date.

Moving 10k members to another usergroup would be a pain ... correct ? .

Looking forward to your feedback and thanks in advance!

pretty sure there was a mod, not able to find it ...