Layered Insecurity
Steven M. Bellovin · IEEE Security & Privacy · 2019
Our systems are layered. Our security isn’t—and that’s a problem. About 25 years ago, in Firewalls and Internet Security, Bill Cheswick and I noted that firewalls are ineffective against attacks at higher levels of the network stack. It turns out that that principle applies to lower levels, too, and to far more than firewalls. Any security mechanisms are utterly dependent on the behavior of other layers of the system, and most of the time, we don’t even know what those layers are, let alone how they behave.