Base Linux Security with IPTables
Most people think that to protect computer networks from outside attacks by using firewall but they don’t understand what a firewall is and how it really work. A firewall inspects packets as they arrive on an interface, searching a table until it finds a matching rule to determine what is should do with each packet and the follow the action the rule specifies.
If the packet does not match a specific rule, a default action decides the packet’s fate, generally known as falling through the bottom of the rules. For firewalls, the generally accepted good default action is Deny. That is, unless we explicitly permit a particular access, the packet is dropped. This allows us to permit what we know and block what we do not. … continue reading : Base Linux Security with IPTables.
