[cod] CoD2 UDP flood

Thu Feb 23 10:06:29 EST 2012

iptables --flush

/sbin/iptables -N QUERY-BLOCK
iptables: Chain already exists.

/sbin/iptables -N QUERY-CHECK
iptables: Chain already exists.

Any help? =)

On Thu, Feb 23, 2012 at 10:03 AM, Marco Padovan <evcz at evcz.tk> wrote:

>  The
>
> "Chain already exists." error should appear...
>
> iptables --flush
>
> then run the script...
>
> eventually run all the rules one by one and see which one is giving you
> the error...
>
> you can monitor the number of blocked packets issuing:
>
> iptables -nvx -L QUERY-BLOCK
>
> and
>
> iptables -nvx -L QUERY-CHECK
>
> Il 23/02/2012 15:53, escapedturkey ha scritto:
>
> # 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.
> /sbin/iptables -N QUERY-BLOCK
> /sbin/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.
> /sbin/iptables -N QUERY-CHECK
> /sbin/iptables -A QUERY-CHECK -p udp -m string ! --string "getstatus"
> --algo bm --from 32 --to 41 -j RETURN
> /sbin/iptables -A QUERY-CHECK -p udp --sport 0:1025 -j DROP
> /sbin/iptables -A QUERY-CHECK -p udp --sport 3074 -j DROP
> /sbin/iptables -A QUERY-CHECK -p udp --sport 7777 -j DROP
> /sbin/iptables -A QUERY-CHECK -p udp --sport 27015:27100 -j DROP
> /sbin/iptables -A QUERY-CHECK -p udp --sport 25200 -j DROP
> /sbin/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.
> /sbin/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.
> # /sbin/iptables -A QUERY-CHECK -m hashlimit --hashlimit-mode srcip
> --hashlimit-name getstatus --hashlimit-above 2/second -j QUERY-BLOCK
> # CentOS 5 or CentOS 6 compatible
> /sbin/iptables -A QUERY-CHECK -m hashlimit --hashlimit-mode srcip
> --hashlimit-name getstatus --hashlimit 2/s -j RETURN
> /sbin/iptables -A QUERY-CHECK -j QUERY-BLOCK
> # look at all the packets going to q3/cod*/et/etc servers
> # /sbin/iptables -A INPUT -p udp --dport 27960:29000 -j QUERY-CHECK
> /sbin/iptables -A INPUT -p udp --dport 27000:30000 -j QUERY-CHECK
>
>  ./spamblock.bsh
> iptables: Chain already exists.
> iptables: Chain already exists.
>
>  iptables -L -n
> Chain INPUT (policy ACCEPT)
> target prot opt source destination
> QUERY-CHECK udp -- 0.0.0.0/0 0.0.0.0/0 udp dpts:27000:30000
>
> Chain FORWARD (policy ACCEPT)
> target prot opt source destination
>
> Chain OUTPUT (policy ACCEPT)
> target prot opt source destination
>
> Chain QUERY-BLOCK (1 references)
> target prot opt source destination
> DROP all -- 0.0.0.0/0 0.0.0.0/0 recent: SET name: blocked-hosts side:
> source
>
> Chain QUERY-CHECK (1 references)
> target prot opt source destination
> RETURN udp -- 0.0.0.0/0 0.0.0.0/0 STRING match !"getstatus" ALGO name bm
> FROM 32 TO 41
> DROP udp -- 0.0.0.0/0 0.0.0.0/0 udp spts:0:1025
> DROP udp -- 0.0.0.0/0 0.0.0.0/0 udp spt:3074
> DROP udp -- 0.0.0.0/0 0.0.0.0/0 udp spt:7777
> DROP udp -- 0.0.0.0/0 0.0.0.0/0 udp spts:27015:27100
> DROP udp -- 0.0.0.0/0 0.0.0.0/0 udp spt:25200
> DROP udp -- 0.0.0.0/0 0.0.0.0/0 udp spt:25565
> DROP all -- 0.0.0.0/0 0.0.0.0/0 recent: UPDATE seconds: 30 hit_count: 1
> name: blocked-hosts side: source
> RETURN all -- 0.0.0.0/0 0.0.0.0/0 limit: up to 2/sec burst 5 mode srcip
> QUERY-BLOCK all -- 0.0.0.0/0 0.0.0.0/0
>
>  Should I be concerned with " iptables: Chain already exists."?
>
>
> On Thu, Feb 23, 2012 at 9:44 AM, Marco Padovan <evcz at evcz.tk> wrote:
>
>>  sure, do it :)
>>
>> Il 23/02/2012 15:44, escapedturkey ha scritto:
>>
>> I support most Q3 engine games. Some go beyond the range specified in the
>> original post.
>>
>>  Can I change:
>>
>>  iptables -A INPUT -p udp --dport 27960:29000 -j QUERY-CHECK
>>
>>  To:
>>
>>  iptables -A INPUT -p udp --dport 27000:30000 -j QUERY-CHECK
>>
>>  Or will that cause problems?
>>
>>  Ex: JK2 =28070 JA = 29070
>>
>> On Thu, Feb 23, 2012 at 9:30 AM, Marco Padovan <evcz at evcz.tk> wrote:
>>
>>>  Let us know if that works ;)
>>>
>>> Il 23/02/2012 15:20, escapedturkey ha scritto:
>>>
>>> Thank you. Much appreciated. =)
>>>
>>> On Thu, Feb 23, 2012 at 7:33 AM, Marco Padovan <evcz at evcz.tk> wrote:
>>>
>>>>  Ehm,
>>>> nope :D
>>>>
>>>> You need all the lines John posted:
>>>>
>>>> http://icculus.org/pipermail/cod/2012-January/015861.html
>>>>
>>>> To make it works in centos5 / 6 change into that ruleset:
>>>>
>>>> iptables -A QUERY-CHECK -m hashlimit --hashlimit-mode srcip
>>>> --hashlimit-name getstatus --hashlimit-above 2/second -j QUERY-BLOCK
>>>>
>>>> in this way (two different lines):
>>>> iptables -A QUERY-CHECK -m hashlimit --hashlimit-mode srcip
>>>> --hashlimit-name getstatus --hashlimit 2/s -j RETURN
>>>> iptables -A QUERY-CHECK -j QUERY-BLOCK
>>>>
>>>>  all the other rules should be kept as they are :)
>>>>
>>>> Il 23/02/2012 13:10, escapedturkey ha scritto:
>>>>
>>>> Thank you. I missed those lines.
>>>>
>>>>  Here is what I have so far:
>>>>
>>>>  /sbin/iptables -N QUERY-BLOCK
>>>> /sbin/iptables -A QUERY-BLOCK -m recent --set --name blocked-hosts -j
>>>> DROP
>>>> /sbin/iptables -A QUERY-CHECK -m hashlimit --hashlimit-mode srcip
>>>> --hashlimit-name getstatus --hashlimit 2/s -j RETURN
>>>> /sbin/iptables -A QUERY-CHECK -j QUERY-BLOCK
>>>>
>>>>  Is this correct?
>>>>
>>>>  Thank you again. =)
>>>>
>>>> On Thu, Feb 23, 2012 at 5:32 AM, Marco Padovan <evcz at evcz.tk> wrote:
>>>>
>>>>>  did you issued all the other commands?
>>>>>
>>>>> like:
>>>>>
>>>>>  iptables -N QUERY-BLOCK
>>>>> iptables -A QUERY-BLOCK -m recent --set --name blocked-hosts -j DROP
>>>>>
>>>>>  ?
>>>>>
>>>>> Il 23/02/2012 03:54, escapedturkey ha scritto:
>>>>>
>>>>> iptables v1.4.7: Couldn't load target
>>>>> `QUERY-BLOCK':/lib64/xtables/libipt_QUERY-BLOCK.so: cannot open shared
>>>>> object file: No such file or directory
>>>>>
>>>>>  Any ideas?
>>>>>
>>>>>
>>>>>  On Wed, Feb 22, 2012 at 4:51 PM, Marco Padovan <evcz at evcz.tk> wrote:
>>>>>
>>>>>>  on centos5 and centos6
>>>>>>
>>>>>> modifying this line:
>>>>>>  iptables -A QUERY-CHECK -m hashlimit --hashlimit-mode srcip
>>>>>> --hashlimit-name getstatus --hashlimit-above 2/second -j QUERY-BLOCK
>>>>>>
>>>>>> in this way (two different lines):
>>>>>> iptables -A QUERY-CHECK -m hashlimit --hashlimit-mode srcip
>>>>>> --hashlimit-name getstatus --hashlimit 2/s -j RETURN
>>>>>> iptables -A QUERY-CHECK -j QUERY-BLOCK
>>>>>>
>>>>>> should mimic the same behaviour
>>>>>>
>>>>>> Il 22/02/2012 18:43, Geoff Goas ha scritto:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> On CentOS 5.5, *--hashlimit-above* is not a valid option for the
>>>>>> "hashlimit" match. Which version of iptables introduces this, and how can I
>>>>>> mimic that same ruleset with the options available to me in version 1.3.5
>>>>>> of iptables?
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> On Fri, Jan 20, 2012 at 7:51 PM, John <lists.cod at nuclearfallout.net>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
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> *Geoff Goas
>>>>>> Systems Engineer*
>>>>>>
>>>>>>
>>>>>>
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>>>>>>
>>>>>>
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>>>>>>
>>>>>>
>>>>>
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