3. What is a proxy?

A proxy is an «intermediate link» for your requests on the Internet that allows you to change the source of the request visible to the recipient, cache data, filter traffic, or distribute the load between servers. A proxy accepts a request, forwards it to the target resource and returns responses back.

Main types of proxies

• Forward-proxy (direct). Works on behalf of the client. Requests are sent first to the proxy and then from it to the target resources. It is used for filtering, caching, restricting access or masking client IP. Usually requires explicit configuration on the user side.
• Reverse-proxy. Located in front of one or more backend servers. Receives requests from users, distributes them between servers, can perform load balancing, caching, access checking, protection against attacks and TLS-termination.
• By level of anonymity:
  • Transparent – does not hide the client’s real IP, often used to intercept traffic without configuring it on the client.
  • Anonymous / distorting – hides the IP, but tells the target server that the request is through a proxy, or substitutes a dummy IP.
  • Elite / high-anonymity – hides both the client’s IP and the fact of using a proxy. In practice, full anonymity is possible only with additional protection against leaks (DNS, WebRTC, behavioral signatures).

Real-life applications

Proxies are used to:

• speeding up page loading through caching;
• load balancing between servers;
• protecting web applications from attacks;
• implementing corporate access policies (site restriction, traffic control).