[cod] CoD2 UDP flood

[B.M. Schiltmans]

If you're using hlsw as rcon-tool, then yes I noticed that too.
Since hlsw is querying your server at quite a high rate, your filters 
start dropping traffic. Ergo, no query-result and no rcon.
When you shut hlsw down, your filters relax and you can connect again.
Not sure if the query-interval is settable in hlsw, but you could always 
try setting your filters a little less strict.

Hope that helps.

Grtz
Bram

On 28-1-2012 20:35, Andrej Parovel wrote:
> 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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