A proxy is a well-known technology in the market, although sometimes it is not well understood how it works. For this reason, this time we will explain what a proxy is and what its usefulness is. But before I start talking about the logical structure of proxy servers, I consider it important to clarify how it is physically implemented in a network environment, so for this part of the explanation please note the following topology:
What is a Proxy?
Proxy servers are generally used as a bridge between the source and destination of a request. In our image, you can see that the computer needs to go through the proxy server to access the Internet, and this is one of the common uses of proxy servers.
For this article, let’s take the example of a fictitious company called ACME SA. In ACME there is a server that allows you to browse the Internet, a proxy server, and without it you cannot browse at all. Therefore, all computers on the network must have their browser’s proxy address and port configured for Internet access to take place.
If any device tries to browse the Internet without these settings, access will not be allowed.
What is a proxy server for?
In this case, the proxy can fulfill some of the following functions:
- Access control: Proxy server administrators may or may not allow certain users to access the Internet through restrictions on their own login or IP addresses, providing the environment with an additional layer of protection.
- Content Filtering: Being in the middle of the road, the server also allows, or not, access to certain sites. Among the rules that can be applied are those to block specific websites, being able to block entire categories.
Example: the user Carefree da Silva is an employee of the ACME company, who can generally surf the Internet through the proxy, since his user has permission to do so. At a certain time of day, Mr. Carefree tries to access the Facebook site and receives a blocking message indicating that access to the social network is blocked. After a few hours a day, Carefree tries to access a few more sites, including some related to investing, but they are all blocked and displaying the message that the Investment / Finance category is not allowed.
In the case of Facebook, only one site was blocked, while in the case of sites intended for the financial market, all are blocked considering that the entire category is part of the blocking rule.
- Caching: Another very common use for Web Proxies is to get them to cache. This causes the proxy, after accessing a page, to store its content on your system. After that, the other requests to this same page will not have to go to the Internet, because the content is already stored in the memory of the proxy.
To illustrate, Mr. Carefree accesses a website called www.123.com. Since the server was configured to cache, it stores all the content that Mr. Carefree accessed. After a few minutes, another user, Mr. Calm, also wants to access the same site (www.123.com). When you try to log in, the proxy doesn’t even search the internet to respond to the page request, as it has everything in memory and displays the stored site for Mr. Quiet, thus saving ACME internet usage.
These are widely used functions of a web proxy server and illustrate a commonly used scenario for most companies.
Another very common use is reverse proxy servers. In the previous examples, the origin of the connection was always within the network, going through the proxy to the Internet. In the case of the reverse proxy, the origin of the requests is on the Internet and seeks to access a server within the environment.
- Load Balancing: Because the structure of the reverse proxy server allows you to connect to multiple destination servers, you can route requests to each one without overloading any one. As another security feature, Internet requests will know only the IP address of the proxy and not all the servers and pages that the company has.
- Cache: As in the web cache example, proxy servers are also used to optimize requests between source and destination. The reverse proxy server stores page elements stored on internal servers, checking for content updates from time to time, so that page servers receive even fewer network requests, allowing them to function even better.
Proxy for everyone
We can’t talk about proxy without talking about free proxies. They are web pages, like https://catsyproxy.com/, that provide addresses ofaround the world “absolutely free”. Anyone on the Internet can make the appropriate settings in their browser and use the server offered to browse the web.
If the question is why someone might want this, the answers are diverse. Using a proxy means that all requests are made by the proxy server, not by your Internet link, that means that your Internet service provider (ISP) does not know what Internet destinations you are going to.
Warning: the phrase “totally free” is in quotation marks because, in general, companies and people who offer fully open proxy servers on the Internet are making some kind of profit. It is important to remember that, although the ISP does not have access to the addresses you access, the proxy server knows everything that users do and can use this information for the most diverse purposes, such as distributing advertising, intercepting content to perform analysis of behavior, collect information and other purposes, malicious or not.