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Blocking RPC portsBlocking RPC portsPosted Apr 3, 2003 16:31 UTC (Thu) by cwong15 (guest, #3013)Parent article: Relaxing with the XDR Vulnerability It's not that straightforward to block RPC ports. There is no such thing as a standard "RPC port". The portmapper provides a sort of a directory service, but each and every RPC service individually has their own port, often both UDP and TCP. And these ports are assigned seemingly randomly as each service starts, with both privileged (if the app is running as root) and high-numbered nonprivileged numbers possible. Blocking these randomly assigned ports is a nontrivial exercise. An attacker can theoretically bypass the portmapper and simply scan for open RPC ports. Chris
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