Hackers Beware

TCP/IP Concepts

In most cases, when two computers want to communicate, the underlying protocols they use are either TCP or UDP and IP. The following is a list of the seven layers in the OSI model that are used for communication:

7) Application

6) Presentation

5) Session

4) Transport

3) Network

2) Datagram

1) Physical

For our discussion, we are concerned with layers 3 and 4. TCP and UDP are at layer 4, the transport layer. IP resides at layer 3, the network layer. So, whether you use TCP or UDP, you still use IP as your layer 3 protocol. TCP is reliable and UDP is unreliable. With session hijacking, because we are concerned with sessions or connection-oriented applications like telnet and FTP, we are also concerned with TCP.

TCP

Because TCP ...