Cisco Networking Simplified, Second Edition

Chapter . Deep Packet Inspection: Controlling Unwanted Applications

How Do You Catch a Criminal When Everyone Wears a Mask?

Traditional firewalls can be very effective against network intrusions in which packets are sent from an untrusted network to a trusted one. The IP protocol being used can be checked for appropriateness and to ensure that it is part of a conversation that originated from the trusted side. In this way, security attacks that rely on manipulating certain IP protocols can be halted.

Increasingly, the number of IP protocols used on the network and the Internet is narrowing dramatically. With the popularity of TCP/IP applications, and even more so web-based applications using HTTP, the vast majority of traffic on modern networks ...