Re: Apache DoS Attack

From: Pim van Riezen (pimat_private)
Date: Tue Aug 11 1998 - 21:48:31 PDT

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    Jonathan Freeman wrote:
    >
    > We just tested the Sioux (Apache DoS) bug on:
    >
    >     <>    IIS 3.0  (Service Pack 3)
    >
    >                causes immediate jump to 100% CPU for approx. 5 seconds
    >                multiple attacks can keep the CPU in the 90% range
    >
    >     <>    IIS 4.0  (Service Pack 3)
    >
    >                causes immediate jump to 80% CPU for approx. a half second
    >                multiple attacks DO NOT cause more thank 40% sustained CPU
    > range
    >
    >     <>    Apache 1.1.1 (Unix)  (Caldera OpenLinux)
    >
    >                causes jump to 66% CPU for each get request and attempts
    >                to use all available swap space for memory.  Can be DoS'd
    > easily.
    >
    >     <>     WebSitePro 2.3.4  (Service Pack 3)
    >
    >                causes immediate jump to 99% CPU for approx. 5 seconds
    >                unknown if DoS would be possible for multiple attacks
    
    Is there any good reason for any of these programs to merge headers
    internally in the first place? I'm wonder because I am actually working
    on a webserver and noted that the code wasn't vulnerable because of the
    way I chose to implement header-handling (which didn't include any
    header-merging code). I wonder if there are any situations where a
    client legitimately sends two headers of the same type (in which case I
    would have to add header-merging code) or is this following conventions
    for the sake of following conventions (in which case I might feel
    inclined to stay lazy :-)? Input is welcome.
    
    Regards,
    
    Pim van Riezen
    
    --
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