more-specifics via IX

[Bradley Urberg Carlson]

I have a few customers' customers, who appear at a local IX.  Due to 
the MLPA-like nature of the IX, I hear their prefixes both at the IX 
and via my own transit customers.  I normally use localpref to prefer 
customer advertisements over peers' advertisements.

There is a customer's customer who is advertising more-specifics at the 
IX (and using a different source AS, to boot).  I can think of a couple 
ways to prevent hearing these, but thought I should ask for suggestions 
first.

-Bradley