Taking Routers Off Their Meds: Why Assumptions Of Router Stability Are Dangerous

In this work, we examine how an adversary in control of a BGP speaker in a transit AS can cause a victim router in an arbitrary location on the Internet to become unstable. Through experimentation with both hardware and software routers, we look at the behavior of routers under abnormal conditions and come to four conclusions. First, routers placed in certain states behave in anything but a stable manner. Second, unexpected but perfectly legal BGP messages can place routers into those states with disconcerting ease. Third, an adversary can use these messages to disrupt a victim router to which he is not directly connected. Fourth, modern best practices do little to prevent these attacks.