Re: RPC/TCP Record Marking for IDS Evasion

From: Dug Song (dugsongat_private)
Date: Fri Jan 11 2002 - 21:55:54 PST

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    On Thu, Jan 10, 2002 at 06:34:38PM -0800, diphenat_private wrote:
    
    > I'm doing some work on parsing RPC protocols as part of my job, and I'm
    > wondering if I've come up with a previously-unknown way of evading IDS
    > for RPC-based attacks.
    
    i mentioned (and implemented) this about two years ago. Robert Graham
    subsequently fixed this in his NetworkICE product, not sure about others:
    
    	http://archives.neohapsis.com/archives/ids/2000-q1/0007.html
    	http://archives.neohapsis.com/archives/ids/2000-q1/0149.html
    
    > what if I split my attack into 5-byte chunks, with 4 bytes of Record
    > Marker between them? Theoretically (untested) a proper RPC
    > implementation on a system shouldn't have any trouble dealing with
    > this...
    
    yes, this works, if done properly. :-)
    
    > The fragmentation and insertion of RMs is only known to the RPC
    > implementation on the target machine.
    
    not true. there isn't really any ambiguity to exploit in simple RPC
    fragmentation, it's just more processing the monitor needs to do.
    
    -d.
    
    ---
    http://www.monkey.org/~dugsong/
    



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