and you are kinda peotected by the community not being well-known,
i.e. different for each upstream. the attacker has to know the
community for each upstream and be able to not only inject the prefix
but also tag it with the correct community for each upstream.
Your argument comes down to "security through obscurity"
no. non-transitiveness through local naming, the reason this has not
allowed serious damage in current practice.
randy