How to test if SYN and FIN are both dropped at the same time in hping3?

Posted by snow on Server Fault See other posts from Server Fault or by snow
Published on 2011-02-04T04:58:45Z Indexed on 2011/02/04 7:27 UTC
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iptables

One of the rules to prevent unexpected attack is to prevent SYN & FIN being used together.

SYN and FIN are both set

$IPT -A INPUT -p tcp --tcp-flags SYN,FIN SYN,FIN -j DROP

How do I use hping to test if this iptable rule works? hping3 192.168.7.0 --keep -S -F??? Is this complete?

When just type iptables -L, it shows:

Chain INPUT (policy DROP) target prot opt source destination
ACCEPT all -- anywhere anywhere
DROP tcp -- anywhere anywhere tcp flags:FIN,SYN/FIN,SYN

WHY do I need to put the "SYN,FIN" twice before drop? Is it because one for source and one for destination?

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