:attr_accessible to protect all attributes

Hi,

I would like to protect all the attributes of one of my model. This
ticket talks about this issue: http://dev.rubyonrails.org/ticket/9631 ,
and a patch to the documentation was submitted:
http://dev.rubyonrails.org/changeset/8032 , which actually states that
defining :attr_accessible alone, means all attributes are protected.

However when I look at the rails API page for attr_accessible, I can't
find the documentation about that:
http://api.rubyonrails.org/classes/ActiveRecord/Base.html#M001981

As of Rails 2.2.2, how do I protect all attributes of my model?

Best regards,