This article was originally published on AI Study Room. For the full version with working code examples and related articles, visit the original post.

Network Security Fundamentals

Network Security Fundamentals

Network Security Fundamentals

Network Security Fundamentals

Network Security Fundamentals

Network Security Fundamentals

Network Security Fundamentals

Network Security Fundamentals

Network Security Fundamentals

Network security protects the communication channels between systems. As organizations move to the cloud and adopt zero-trust architectures, traditional perimeter-based network security is giving way to more granular, identity-aware approaches. This article covers the foundational concepts every developer and security practitioner needs.

Firewalls

Firewalls filter network traffic based on pre-defined rules. They are the first line of defense in network security.

Packet Filtering Firewalls

Packet filtering firewalls inspect individual packets against rule sets. They examine source and destination IP addresses, ports, and protocols. They operate at layers 3 and 4 of the OSI model.

Rule table example:

Source IP Dest IP Port Protocol Action

10.0.1.0/24 10.0.2.0/24 443 TCP Allow

0.0.0.0/0 10.0.1.5 22 TCP Deny

Stateful Firewalls

Stateful firewalls maintain a connection table. They track the state of active connections and make decisions based on the connection state, not just individual packets. This allows them to permit return traffic for legitimate outbound connections while blocking unsolicited inbound traffic.

Next-Generation Firewalls (NGFW)

NGFWs combine traditional firewall capabilities with application-layer inspection, intrusion prevention, and threat intelligence. They can identify applications regardless of port or protocol and enforce policies based on user identity.

iptables stateful rule example

iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

iptables -A INPUT -m state --state NEW -p tcp --dport 443 -j ACCEPT

iptables -A INPUT -m state --state NEW -p tcp --dport 80 -j ACCEPT

iptables -A INPUT -j DROP

Virtual Private Networks (VPNs)

VPNs create encrypted tunnels between endpoints over untrusted networks. They extend a private network across a public network, allowing remote users and branch offices to access internal resources.

Site-to-Site VPN

Connects entire networks to each other, such as an office to a cloud VPC. AWS VPN, Azure VPN Gateway, and GCP Cloud VPN all implement IPsec tunnels.

AWS CLI: create a VPN connection

aws ec2 create-vpn-connection \

\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\--customer-gateway-id cgw-123 \

\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\--vpn-gateway-id vgw-456 \

\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\--type ipsec.1

---

Read the full article on AI Study Room for complete code examples, comparison tables, and related resources.

Found this useful? Check out more developer guides and tool comparisons on AI Study Room.