Library /sys$common/syshlp/nclhelp.hlb restrict  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Places the Session Control module in the restrict state. In this
    state, outgoing connection requests are accepted. Incoming connection
    requests are not accepted, unless the client has sufficient privilege to
    override.

    restrict  [node node-id] session control