Assign Rule To New Registered User

hi dears!

First of all sorry for my bad english .

i have a test project with Yii. I use "yii-user" extension for user management and "Auth" extension for grant access to users.

then I was create a Role - Named "registered_user" - and I want to Assign this Role to new user after egistration.

But I dont want modify "yii-user" module Code. please suggest a solution. What is The Best solution!?

can i attach a behavior to User Model Without Modifying User Model Class Code??