Packet Filtering

This article explains packets, packet headers, and packet filtering. What can the option of allowing or disallowing packets be based on? What are the weaknesses and advantages of packet filtering? After you read, you should be able to describe packets and packet headers.

7. Lessons learned


We have learned that:

  1. A firewall can be a risk in itself. A badly configured firewall is worse than not having one at all.
  2. How to setup a basic gateway and a transparent proxy.
  3. The key to a good firewall is to know the protocols you want do allow.
  4. That IP traffic does not always contain legitimate data, e.g. ICMP packets, which can contain a malicious payload.
  5. How to prevent SYN attack.
  6. Filtering HTTP traffic by removing offensive pictures and downloads of viruses.
  7. Combining packet filters and application gateways provides better control.

Now, if you really need to, go create a firewall that matches your needs.