Re: DoS "Probing" on one of our hosts

From: Chris Calvert (chris_at_idaemon.ca)
Date: 06/30/03

  • Next message: Edward Balas: "Re: DoS "Probing" on one of our hosts" 
    To: chris@de-punkt.de
Date: 30 Jun 2003 07:32:01 -0600

    Hi Chris

    DoS attack duration can vary considerably. I've seen attacks that last
    over a day or two, it really depends on how persistent the attacker is
    and how robust the target is. 100 Mbit attacks might bring down a small
    hosting service, or get shrugged off by a target on a larger pipe.

    Get a capture of the traffic and do some analysis. If you are being
    hammered with a connectionless protocol such as UDP or ICMP then there
    is no way for you, the destination of the traffic, to determine the
    source if it has been spoofed, however you might be able to get useful
    data from a capture regardless. Try tools such as Ethereal,for a bit of
    help analyzing the traffic. For example, you might be getting hit with
    huge packets which saturate your Internet connection and/or inbound
    interface, or you may be getting hit with small packets but at a
    packet/second rate that your switch, modem, interface, or whatever
    cannot handle. There may be no signatures to detect, you might simply
    be the target of a brute force traffic DoS.

    Regards,

    Chris

    On Sun, 2003-06-29 at 14:41, Christopher Kunz wrote:
    > Hey,
    >
    > we have been encountering three short DoS attacks during the weekend -
    > each one around 1 hour in length and with about 100mbit worth of
    > bandwidth. So far, we've yet to determine even the most basic stuff,
    > since we don't seem to have any logging. I have two questions regarding
    > this:
    > 1. isn't one hour a pretty short time for a DoS? I've seen attacks on
    > other nets lasting for hours, sometimes up to a day...
    > 2. is there any tool to determine the source IPs of the attack (even if
    > they're spoofed, I'd like to see _anything_)? Snort sits on the attacked
    > host and happily reports SQL/Slammer and other trivial stuff, but goes
    > through one of the attacks without picking any signatures up.
    >
    > Regards,
    >
    > --ck 

    -- 
Chris Calvert <chris@idaemon.ca>
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  • Next message: Edward Balas: "Re: DoS "Probing" on one of our hosts"

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