Leds-
I tend to agree with the one other post that made it to the list
re your question. I would assume that your various security devices are
capable of generating rather detailed logs. Cull that information to get an
idea of the number of possible problems that were prevented. Take nimda for
example. Estimate the cost (in time, lost productivity, etc) of a nimda
infection to your organization. Then extrapolate that out to the number of
incidences that were deterred. Although overly simplified here, it seems to
that this sort of strategy would prove effective.
-Q-