— The Internet’s interdomain routing protocol, BGP, is vulnerable to a number of damaging attacks, which often arise from operator misconfiguration. Proposed solutions with strong guarantees require a public-key infrastructure, accurate routing registries, and changes to BGP. However, BGP routers can avoid selecting and propagating these routes if they are cautious about adopting new reachability information. We describe a protocolpreserving enhancement to BGP, Pretty Good BGP (PGBGP), that slows the dissemination of bogus routes, providing network operators time to respond before problems escalate into largescale Internet attacks. Simulation results show that realistic deployments of PGBGP could provide 99% of Autonomous Systems with 24 hours to investigate and repair bogus routes without affecting prefix reachability. We also show that without PGBGP, 40% of ASs cannot avoid selecting bogus routes; with PGBGP, this number drops to less than 1%. Finally, we show that PGBGP is inc...