Assign Custom Permission Levels in User Information List

1)To Add permissions in User Information List browse
server/_catalogs/users/detail.aspx
2)right click on any user name link -->copy shortcut-->to get User Information List id
/_Layouts/listform.aspx?PageType=x&ListId={Guid}&ID=y
3)form the URL
_layouts/listedit.aspx?List=guid obtained as above
4)In Permission Settings add the Group having Custom Permission
5)Create the custom permission level as shown in following Image

6)you may need to add the custom permission levels for discussion board or to let the ad authenticated user modify there user info,in user information list
1)by default AD authenticated user don't have permissions to edit all the lists
so break the permissions for this list and create custom permissions for ad-authenticated user and add to User Information List
2)same is the case for discussion boards