For the July 19th Code Red incident, I posted a theory of the worm that said it
had random spread with a spread rate of about 1.8 hosts per hour, and showed
this analytic model approximately accounted for the observed growth in the worm
probe rate.

I applied the same model in a quick first-cut analysis to today's events, and
again it seems to fit except with a lower spread rate of about 0.7 hosts per
hour. The worm has now pretty much saturated. This suggests that there were a
little less than half as many vulnerable hosts as last time.

This is an interesting way of working with these incidents, as I was able to
estimate the spread rate fairly well before there was any sign of saturation,
and thereby predict approximately when it would saturate, and approximately how
many hosts would get compromised relative to last time.

The graphs are at

http://www.silicondefense.com/cr/aug.html

Stuart.

-- 
Stuart Staniford     ---     President     ---     Silicon Defense
         ** Silicon Defense: Technical Support for Snort **
mailto:stuartsilicondefense.com  http://www.silicondefense.com/
(707) 445-4355 x 16                           (707) 445-4222 (FAX)
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