Transitive trust

[Duan Zhenhai <ccdzh @ shoukui . pku . edu . cn>]

Hi,

    How can we prevent transitive trust?
    I think a stronger user level authentication is one idea. But 
    obviously,There are some other conditions where we could not  use
    user authentication, What we can control is ip address domain.

    any comment is appricated.

    Duan Zhenhai
    Peking University