Understanding TCP Reset Attacks, Part I

A vulnerability in TCP, the transmission control protocol, recently received some exposure in the media. Paul Watson released a white paper titled Slipping In The window: TCP Reset Attacks at the 2004 CanSecWest conference, providing a much better understanding of the real-world risks of TCP reset attacks.

To better understand the reality of this threat, KernelTrap spoke with Theo de Raadt, the creator of OpenBSD, an operating system which among other goals proactively focuses on security. In this article, we aim to provide some background into the workings of TCP, and then to build upon this foundation to understand how resets attacks work.

This is the first article in a two part series. The second article will look into how TCP stacks can be hardened to defend against such attacks. Toward this goal, we spoke with members of the OpenBSD team to learn what they have done so far, and what further plans they have to minimize the impact of reset attacks.