Single logon from vbulletin to drupal

hi all

I am using vbulletin 4.0.2 and DP 6.x and I am looking for a module that transfer vbulletin user to drupal user that a user logon into vbulletin that the also logon in drupal - as single logon from vbulletin.

Could you help me about this module in drupal?

Thanks in advance.