RPC Filtering

• Only fixed port is that of portmapper, 111
• All initial RPC calls are addressed to this
• Portmapper should be blocked to external access because it is a security risk by itself
• External process can still scan all ports looking for RPC servers
• Most common RPC services use UDP, so can only block by blocking all UDP.
• Use TCP for RPC if you need to use RPC through firewall