Re: HTTP DDoS attack on our servers

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To: "Markus Peter" <warp@spin.de>, <incidents@securityfocus.com>
Date: Wed, 9 Jul 2003 12:26:05 -0700

What were you running on that port? Or did I misunderstand you?

--
Regards,
Tim Greer  chatmaster@charter.net
Server administration, security, programming, consulting.
----- Original Message -----
From: "Markus Peter" <warp@spin.de>
To: <incidents@securityfocus.com>
Sent: Tuesday, July 08, 2003 6:06 AM
Subject: HTTP DDoS attack on our servers
> Hello
>
> Since yesterday, about 8pm CET, we observe a strange phenomenon on one of
> our servers, which appears like a DDoS attack. The characteristics do not
> match those of the typical known UDP DDoS tools but is TCP based.
>
> Basically, > 8.000 IP numbers are sending HTTP requests to our server on a
> non-HTTP port (8000), which ran an entirely different, not HTTP related
> service on this machine. The IP numbers are mostly assigned to Europe and
> North America.
>
> The requests always look the same way:
>
> GET /index.htm HTTP/1.1
> Accept: */*
> User-Agent: UserAgent
> Connection: close
> Host: <our ip number>
>
> Please note that they literally supplied "UserAgent" as User-Agent - I
only
> removed our ip number from the requests. Each attacking host opens
multiple
> connections per second. Even though the server which ran at 8000 could not
> handle HTTP requests at all and immediately closed the connection after
the
> first sent line, the sheer number of connection attempts was enough to
> basically force us to put the service offline, as we had over 60.000
> concurrent TCP connections due to this.
>
> Due to the above described characteristics, I'm pretty sure that it's not
> just a misguided link on some large website, but some sort of non-browser
> program doing the requests.
>
> We nmapped some of the requesting machines. All of the scanned hosts
appear
> to be running windows, with all of them having TCP port 45836 open. If we
> try connecting to that port, the connection is either immediately closed
> again by the remote end, or occasionally kept open indefinitely, but in
> neither case any data is sent back to us.
>
> I'm now completely puzzled on what is happening and what kind of tool we
> confront. Anyone else experiences incidents like those?
>
> --
> Markus Peter - SPiN AG
> warp@spin.de
>
>
> --------------------------------------------------------------------------
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----------------------------------------------------------------------------
Attend the Black Hat Briefings & Training, July 28 - 31 in Las Vegas, the 
world's premier technical IT security event! 10 tracks, 15 training sessions, 
1,800 delegates from 30 nations including all of the top experts, from CSO's to 
"underground" security specialists.  See for yourself what the buzz is about!  
Early-bird registration ends July 3.  This event will sell out. www.blackhat.com
----------------------------------------------------------------------------

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