Network Security
Packet Filtering
Also known as: Packet filter
Definition
A network-security technique that inspects each packet's header fields and allows or drops it based on a static ruleset.
Examples
- An iptables rule dropping all inbound TCP/23 (Telnet) on a Linux server.
- An access-list on a Cisco IOS router blocking RFC1918 source addresses on the WAN interface.
Related terms
Firewall
A network security device or software that monitors and controls inbound and outbound traffic based on a defined ruleset, separating trusted from untrusted networks.
Stateless Firewall
A firewall that evaluates each packet independently against static rules, without tracking the state of connections.
Stateful Firewall
A firewall that tracks the state of active connections in a connection table and allows return traffic that matches an established session.
Deep Packet Inspection (DPI)
An inspection technique that examines the full payload of network packets — not just headers — to identify applications, content, and threats.
Network Segmentation
Network Segmentation — definition coming soon.
Network Address Translation (NAT)
Network Address Translation (NAT) — definition coming soon.