Network Security Fundamentals Every Developer Must Know

## Why developers need network security knowledge

Modern applications run on interconnected networks. Understanding how those networks work is critical to building secure systems.

Firewall basics

Firewalls control traffic based on rules. At minimum, you should:

• Allow only required ports (e.g., 80/443)
• Deny all incoming traffic by default
• Use network segmentation to isolate sensitive systems

VPNs and secure tunnels

A VPN encrypts traffic over untrusted networks. Use VPNs for:

• Remote access to internal systems
• Secure site-to-site connections

TLS is non-negotiable

Always use HTTPS with strong cipher suites. Never allow mixed content.

Common network vulnerabilities

Open ports Run `nmap` to discover exposed services and close anything unnecessary.

Weak authentication Avoid default credentials and enforce MFA for admin access.

Insecure protocols Replace FTP/HTTP/SMTP with SFTP/HTTPS/SMTPS where possible.

Build security into your deployment pipeline

• Scan your infrastructure as code for misconfigurations
• Use automated tools to detect open ports and weak ciphers
• Monitor traffic for anomalies and suspicious connections