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I check the conections to the server with command "netstat -nlup" and see this

Proto Recv-Q Send-Q Local Address             Foreign Address     
udp     2208      0*   
udp     5888      0*

Many received packets to my server in ports like the example, this cause late responses from the server with other applications in other udp ports. How i can stop this kind of udp flood with iptables?

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Iptables on your system is unlikely to help as if it truly is a DOS attack your bandwidth is being consumed and even if you try to block something on your system the bandwidth is still consumed.

You really need to get your upstream provided to block the relevant IP addresses for you.

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My upstream is normal: rx 1.44 Mbit/s 2362 p/s tx 2.91 Mbit/s 2712 p/s the uplink is 100Mbps, RAM and CPU is ok. – Kiwi Aug 16 '12 at 20:30

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