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Old 01-26-2003, 11:04 AM   #1
Registered: Jan 2003
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Question Closing UDP ports in RHL 8.0

I have set up RHL 8.0 with DHCP and now have been messing with IPTABLES and such to secure the server. I have MASQUERADING set up for my internal LAN. I have changed the policy for input forward and output to drop (does reject not work? I can't use reject it says it isn't a recognized command). I run port scanners from various utilities not on the RHL machine. They always show UDP ports, but everything else shows locked down (TCP for example never shows up).

I have even made chains to deny udp entire range rules and they still show up... what is up with the UDP ports and not shutting down??????
Old 01-26-2003, 12:24 PM   #2
Registered: Feb 2002
Location: Grenoble
Distribution: Debian
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Could you post your iptables lines related to UDP?
Old 01-26-2003, 02:27 PM   #3
Registered: Jan 2003
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This is what I have put into iptables chains.

Although they show closed on web port scanners they are still shown as probed. Am I doing all I can? Can they be shut down to where they aren't even seen? I have tried INPUT policy DROP (is there another policy instead of drop to use?) and when I used DROP I accept port 80 and yet not all web pages work... what am I missing there? This is my current config using ACCEPT.

Chain INPUT (policy ACCEPT)
target prot opt source destination
REJECT tcp -- anywhere anywhere tcp dpt:ssh reject-with icmp-port-unreachable
REJECT tcp -- anywhere anywhere tcp dpt:sunrpc reject-with icmp-port-unreachable
REJECT udp -- anywhere anywhere udp dpt:bootps reject-with icmp-port-unreachable
REJECT udp -- anywhere anywhere udp dpt:sunrpc reject-with icmp-port-unreachable

Chain FORWARD (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination


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