Finding out where a bogus route is coming from?

["Joseph C. Pistritto" <jcp () pointcast com>]

Any hints on how to do this?  

We have a situation where some person has broadcast a route which is
mapping one of our subnets to the wrong place.
I'm trying to track this at the Mae's to find out what's going on, but I'm
really interested in figuring out how
one can prevent this sort of thing or find out the original source of the
bad route.

        -jcp-

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