Best way to deal with bad advertisements?

A good solution would be for providers to only accept routes
registered in a routing database (the IRR) from those authorized to
send them with hierarchical authorization within the database (as
implemented by RIPE) and strong authentication (PGP as implemented by
the RA) and top level authorization based on IANA or delegated address
registry assignments.

But you've heard this before. The best any one provider can do is to
accurately populate the IRR and if possible (based on the limitations
of their routers) put the IRR data into use in defining filters.