Proxies

Proxies

A proxy is when a device or service sits in the middle of a connection and acts as a mediator. The mediator is the critical piece of information because it means the device in the middle must be able to inspect the contents of the traffic. Without the ability to be a mediator, the device is technically a gateway, not a proxy.
Proxies will almost always operate at Layer 7 of the OSI Model. There are many types of proxy services, but the key ones are:

• Dedicated Proxy / Forward Proxy
• Reverse Proxy
• Transparent Proxy

Forward proxy:

Is when a client makes a request and the computer carries out it.
For example, in a corporate network, sensitive computers may not have direct access to the Internet. To access a website, they must go through a proxy (or web filter).

• Web Browsers like Internet Explorer, Edge, or Chrome all obey the "System Proxy" settings by default.
• Firefox does not use WinSock and instead uses libcurl, which enables it to use the same code on any operating system.
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Reverse Proxy

A reverse proxy, is the reverse of a Forward Proxy. Instead of being designed to filter outgoing requests, it filters incoming ones. The most common goal with a Reverse Proxy, is to listen on an address and forward it to a closed-off network.
Another common Reverse Proxy is ModSecurity, a Web Application Firewall (WAF). Web Application Firewalls inspect web requests for malicious content and block the request if it is malicious.
 ModSecurity Core Rule Set, as its a great starting point. Cloudflare, also can act as a WAF but doing so requires letting them decrypt HTTPS Traffic, which some organizations may not want.
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 All these proxy services act either transparently or non-transparently.
 - With a transparent proxy, the client doesn't know about its existence. The transparent proxy intercepts the client's communication requests to the Internet and acts as a substitute instance.
 - If it is a non-transparent proxy, we must be informed about its existence. For this purpose, we and the software we want to use are given a special proxy configuration that ensures that traffic to the Internet is first addressed to the proxy. If this configuration does not exist, we cannot communicate via the proxy.