Re: Nimda Probes Stopped

From: Stuart Staniford (stuartat_private)
Date: Tue Sep 18 2001 - 17:36:26 PDT

  • Next message: Bob Todd: "Our sumary of the NIMDA (CV) worm"

    I guess the picture that's emerging is that the worm has stopped probing in
    some parts of IP-space, but is still probing in others.  That suggests it
    can't have a hard time-based turn off, but could have some other kind of
    limit to how much it scans built in.  We've got several ways of seeing the
    worm in different places, and the probe rate graphs do not appear
    consistent (it's not like Code Red where there was roughly consistent
    behaviour everywhere).
    
    We're still far from understanding the worm code properly, but as far as we
    can tell so far, it only seems to access the system time once (it puts it
    into a registry variable).  It does seem to be keeping track of its own cpu
    time usage for some reason.
    
    Homer Wilson Smith wrote:
    > 
    > > We're still seeing several probes per second into a /17, though the rate is
    > > noisy.  The probe rate is not going up any more - suggesting some degree of
    > > saturation.  Are you sure someone upstream of you didn't apply some filter?
    > >
    >      What kind of filter?
    
    I've heard reports of some ISPs disallowing inbound port 80 syns into some
    portions of their address space.  I wanted to rule out some explanation
    like that.
    
    Stuart.
    
    -- 
    Stuart Staniford     ---     President     ---     Silicon Defense
             ** Silicon Defense: Technical Support for Snort **
    mailto:stuartat_private  http://www.silicondefense.com/
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