[Snort-sigs] HTTP Get Flood

Jamie Riden jamie.riden at ...2420...
Sun Feb 15 11:13:19 EST 2015


I know this is snort list, so forgive me changing the subject slightly.

Last time I dealt with anything on this scale (~12k hosts engaged in DoS by
repeated HTTP GETs) we used fail2ban on the logs and fed this into the
ipset fail2ban target to literally drop the traffic.

(After we made this change, and about another day of hammering us and
getting no particular effect, the attackers gave up. I don't think they
were particularly sophisticated though.)

Of course, you could equally well feed fail2ban from the snort logs and
achieve the same thing that way rather than going off the apache logs as we
were.

However in DoS conditions, the quicker you can drop the traffic the better,
so a "rude" DROP from iptables is preferred to a "polite" 403 message from
Apache, and so on.

cheers,
 Jamie

On 15 February 2015 at 16:03, Mohammad Rastgoo <mohammad at ...4014...> wrote:

> Hi,
>
> This is it:
>
>   Srv PID Acc M CPU SS Req Conn Child Slot Client VHost Request  0-1 21953
> 0/75/3739 _ 0.87 3 128 0 0.28 42.46 92.50.31.242 www.domain.com:80 GET
> /moon HTTP/1.1  1-May 21977 1/39/3034 K 0.98 9 93 0.7 0.31 36.24
> 92.50.31.242 www.domain.com:80 GET /moon HTTP/1.1  13-1 21241 0/168/3311 _
> 2.17 2 130 0 0.41 45.39 46.209.70.74 www.domain.com:80 GET /moon HTTP/1.1
> 15-1 22114 ######## K 0.18 11 93 0.7 0.05 20.92 46.209.70.74
> www.domain.com:80 GET /moon HTTP/1.1  16-1 22186 0/14/3072 _ 0.63 11 88 0
> 0.1 32.13 46.209.70.74 www.domain.com:80 GET /moon HTTP/1.1  19-1 20925
> 0/114/2514 _ 2.49 12 88 0 0.35 30.51 46.209.70.74 www.domain.com:80 GET
> /moon HTTP/1.1  20-1 22275 0/3/3303 _ 0.3 5 129 0 0.02 31.76 46.209.13.250
> www.domain.com:80 GET /moon HTTP/1.1
>
> On Sun, Feb 15, 2015 at 9:00 AM, Al Lewis (allewi) <allewi at ...3865...>
> wrote:
>
>>  Hello,
>>
>>
>>
>>                 Can you provide a sample of the rule/conf you are trying
>> to use as well as a pcap of the offending traffic?
>>
>>
>>
>> The section on uricontent is here:
>> http://manual.snort.org/node32.html#SECTION004523000000000000000
>>
>>
>>
>> Make sure you are not trying to match on content before its normalized as
>> listed in the manual:
>>
>>
>>
>> “The uricontent keyword in the Snort rule language searches the
>> NORMALIZED request URI field. This is equivalent to using the http_uri
>> modifier to a content keyword. As such if you are writing rules that
>> include things that are normalized, such as %2f or directory traversals,
>> these rules will not alert.”
>>
>>
>>
>>
>>
>> Hope this helps.
>>
>>
>>
>>
>>
>> Albert Lewis
>>
>> QA Software Engineer
>>
>> SOURCE*fire*, Inc. now part of *Cisco*
>>
>> 9780 Patuxent Woods Drive
>> Columbia, MD 21046
>>
>> Phone: (office) 443.430.7112
>>
>> Email: allewi at ...3865...
>>
>>
>>
>> *From:* Mohammad Rastgoo [mailto:mohammad at ...4014...]
>> *Sent:* Saturday, February 14, 2015 7:42 PM
>> *To:* snort-sigs at lists.sourceforge.net
>> *Subject:* [Snort-sigs] HTTP Get Flood
>>
>>
>>
>>
>>  Hi,
>>
>> Thanks for reading this.
>>
>> My site has been receiving attacks for a while now and I've been able to
>> stop them using snort + pfsense. Most of them were stopped just by using
>> uri-content in the rule.
>>
>> Today I've been receiving Get attacks on the main page. It really seems
>> too simple but any rule I have tried has not blocked any IP addresses.
>>
>> Would someone please guide me to the right direction?
>>
>> Thanks
>>
>
>
>
> --
> Mohammad Rastgoo
> Founder & CEO
>
>
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-- 
Jamie Riden / jamie at ...3509... / jamie.riden at ...2420...
http://uk.linkedin.com/in/jamieriden
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