[cod] CoD2 UDP flood

[Andrej Parovel]

Hello,

Thank you, I assumed it was these iptables problem, because i had never 
before these problems. With less strict do you mean these line:

iptables -A QUERY-CHECK -m hashlimit --hashlimit-mode srcip 
--hashlimit-name getstatus --hashlimit-above 2/second -j QUERY-BLOCK

to rise up these value (2 second)? Or maybe some other too?

Thank you

Andrej

+386 31 247 707
aparovel at gmail.com


On 28.1.2012 20:52, B.M. Schiltmans wrote:
> 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
>>>
>>>
>>> _______________________________________________
>>> cod mailing list
>>> cod at icculus.org
>>> http://icculus.org/mailman/listinfo/cod
>>
>>
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