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.
1. A firewall
People often think that a firewall provides the ultimate security, but they are wrong. A firewall is also a piece of software and should be treated the same way as any other piece of software, because it is just as likely to contain bugs.
So think before implementing a firewall! Do you really need one? If you think you need one write a policy on how it should work, what type of firewall, and who should operate it. But first, read this guide.
Firewalls are used for two purposes:
- To keep users (worms/attackers) out.
- To keep users (employees/children) in.
Basically, there are three types of firewalls:
- Packet filtering.
- Circuit relay.
- Application gateway.
A firewall should be a dedicated machine running no services (or sshd as the only one) and secured the way this guide recommends it be.