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Broadcasting unwanted UDP messages

DISCUSSION Ken Moore 2 participants 2 messages Apr 19, 2006

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Ken Moore

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Thanks to all those who offered suggestions, It certainly helped me move a little up the learning curve.
I decided to try the iptables solution(figuring a knowledge of iptables will help in future protection from the nasties on the Inet).

The command
"iptables -A OUTPUT -i sm0 -p udp --dport 137 -j DROP" failed but
"iptables -A OUTPUT -o sm0 -p udp --dport 137 -j DROP" worked fine.

However "iptables -L OUTPUT" revealed

"target     prot     opt    source        destination"
"DROP       udp      --     anywhere     anywhere         udp dpt:netbios-ns"

this appears to not identify the "sm0" destination specified in the APPEND command.
I guess I need the netbios for communication with Windoz PC's on my network so this does not look like a fix.
What am I doing wrong?.

Signature · 4 lines
Regards - Ken VK4AKM
         Yeppoon, Queensland
         -= Use Open Source Software =-
                GNU\Linux Debian.
#1 lore raw

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Hi Ken,

Quoted 3 lines · Ken Moore

The command
"iptables -A OUTPUT -i sm0 -p udp --dport 137 -j DROP" failed but
"iptables -A OUTPUT -o sm0 -p udp --dport 137 -j DROP" worked fine.

You can only specify an _output_ interface on the OUTPUT chain, likewise only an _input_ interface works on the INPUT chain.

Quoted 8 lines

However "iptables -L OUTPUT" revealed

"target     prot     opt    source        destination"
"DROP       udp      --     anywhere     anywhere         udp

dpt:netbios-ns"

this appears to not identify the "sm0" destination specified in the APPEND command.

Add a "v" (verbose) to the list command to show interfaces in your rules:
"iptables -vL OUTPUT"

Quoted 2 lines

I guess I need the netbios for communication with Windoz PC's on my network so this does not look like fix.

A question I have for you is, are you actually *using* Samba? Are you sharing a portion of your Linux filesystem or sharing a printer hanging off of your Linux box with Windows clients? If the answer is "no," then you most likely don't need Samba running at all.

73,

Brett, WA7V

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