Proxy is an intermediary that sits between a client (e.g., your browser or an app) and the Internet (or a server). All requests and responses flow through the proxy, which can inspect, filter, cache, or modify traffic on behalf of the client or server.

Proxy ≠ Gateway

A gateway simply forwards at lower layers (e.g., NAT at L3); a proxy must understand and mediate application‑layer (L7) traffic.

Main Proxy Types

1. Forward (Dedicated) Proxy

   • Placed “in front” of clients.
   • Clients must be configured to use it.
   • Common in corporate networks for access control, content filtering, caching, and malware inspection.

2. Reverse Proxy

   • Placed “in front” of servers.
   • Clients think they’re talking to the real server, but the proxy forwards requests to one or more back‑end servers.
   • Used for load balancing, SSL offload, DDoS protection, and web‑application firewall (WAF) functions.

   

3. Transparent vs. Non‑Transparent

   • Transparent Proxy: Clients are unaware—traffic is intercepted without needing client settings.
   • Non‑Transparent Proxy: Clients must be explicitly configured to use the proxy; no config → no access.

Why Use Proxies?

• Security & Filtering:

  • Scan outbound requests for malware or block malicious destinations.

  • Shield internal servers with a reverse proxy/WAF.

• Privacy & Anonymity:

  • Hides clients’ IPs from external sites.

  • Can centralize logging of user activity.

• Performance & Caching:

  • Store frequently accessed content close to clients.

  • Reduce bandwidth and speed up load times.

• Load Distribution:

  • Reverse proxies distribute incoming requests across multiple servers.

  • Enhance availability and reliability.