[cod] CoD2 UDP flood

[Andrej Parovel]

Hello,

Did maybe anybody notice or have the problem when applying iptables 
script witch is in the reply, that you can't then connect on RCON and 
also I can't reach my servers over HSLSW, but you can connect on the 
server and it is actualy running ok.
Just rcon connecting problems and HSLW reaching.

Thank you.

Andrej

+386 31 247 707
aparovel at gmail.com


On 21.1.2012 1:51, John wrote:
> On 1/20/2012 3:27 PM, Marco Padovan wrote:
>> I was referring to dynamic filtering using -m recent
>>
>> [not] to manually adding IPs O.o
>
> Marco's right about this. The most effective way to prevent effects 
> from these attacks on Linux is to use a combination of the "string", 
> "hashlimit", and "recent" modules. Done right, the solution is mostly 
> automatic, so you shouldn't need to manually add IPs.
>
> These commands, for instance, would block external IPs that send 
> queries at a rate of 2/second or higher:
>
> # add a host to the banlist and then drop the packet.
> iptables -N QUERY-BLOCK
> iptables -A QUERY-BLOCK -m recent --set --name blocked-hosts -j DROP
>
> # is this a query packet? if so, block commonly attacked ports outright,
> # then see if it's a known attacking IP, then see if it is sending at 
> a high
> # rate and should be added to the list of known attacking IPs.
> iptables -N QUERY-CHECK
> iptables -A QUERY-CHECK -p udp -m string ! --string "getstatus" --algo 
> bm --from 32 --to 41 -j RETURN
> iptables -A QUERY-CHECK -p udp --sport 0:1025 -j DROP
> iptables -A QUERY-CHECK -p udp --sport 3074 -j DROP
> iptables -A QUERY-CHECK -p udp --sport 7777 -j DROP
> iptables -A QUERY-CHECK -p udp --sport 27015:27100 -j DROP
> iptables -A QUERY-CHECK -p udp --sport 25200 -j DROP
> iptables -A QUERY-CHECK -p udp --sport 25565 -j DROP
> # is it already blocked? continue blocking it and update the counter so it
> # gets blocked for at least another 30 seconds.
> iptables -A QUERY-CHECK -m recent --update --name blocked-hosts 
> --seconds 30 --hitcount 1 -j DROP
> # check to see if it exceeds our rate threshold,
> # and add it to the list if it does.
> iptables -A QUERY-CHECK -m hashlimit --hashlimit-mode srcip 
> --hashlimit-name getstatus --hashlimit-above 2/second -j QUERY-BLOCK
>
> # look at all the packets going to q3/cod*/et/etc servers
> iptables -A INPUT -p udp --dport 27960:29000 -j QUERY-CHECK
>
> The "recent" module makes it possible to block up to 100 IPs at once 
> with this method (any attackers beyond this would only be 
> rate-limited). That number can be raised when the module is loaded, 
> but I haven't seen 100 attacks happening at once yet (typically it's 
> maybe 5-20 at once). You can see blocked hosts later by looking at 
> /proc/net/xt_recent/blocked-hosts.
>
> (If you don't have "recent", you could get away without it -- just be 
> aware that some of the packets will get through, increasing load on 
> the game server. Without "hashlimit", you'd still see an advantage 
> from the port checks, but you'd need to manually block IPs that are 
> being hit on other ports. Without "string", you'd similarly be down to 
> just port checks, and need to take out the other rules.)
>
> -John
>
>
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