Handlers that require access to some of the internal interfaces on the proxy manager have to go through the IInternalUnknown interface. This prevents handler's from blindly delegating and exposing the aggregatee's internal interfaces outside of the aggregate. These interfaces include IProxyManager, IClientSecurity, and IMultiQI. If the handler wants to expose IClientSecurity or IMultiQI, it should implement them itself.
In the case of IClientSecurity, if the client tries to set the security on an interface that the handler has exposed, the handler should set the security on the underlying network interface proxy.
In the case of IMultiQI, the handler should fill in the interfaces it knows about, then forward the call on to the proxy manager to get the rest of the interfaces filled in.