The TCP/IP protocol suite, which is very widely used today,
was developed under the sponsorship of the Department of Defense.
Despite that, there are a number of serious security flaws inherent in the protocols,
regardless of the correctness of any implemenlations. We describe a variety of attacks based on these flaws,
including sequence number spoofing, routing attacks, source address spoofing, and authentication attacks.
We also present defenses against these attacks, and conclude with a discussion of broad-spectrum defednses such as encryption.