how to Block iq stanza with specific namespace

I am making xmpp application in which I used Last activity to implement last seen. I want to give one more feature to disable last seen status to user side so that user's contact can't see user's last seen status. For that I want to use privacy list(XEP-0016) to block iq stanza for specific namespace (iq:last). Here, if we block iq stanza globally it will block all the iq stanza. Please guide me, what should I do.

Thanks in advance...