C koi proxy that has been discussed Hadopi?
A proxy server (French for "proxy server" also called "proxy") is causing a machine acting as an intermediary between the computers in a local area network (sometimes using protocols other than TCP / IP) and Internet.
Most of the time the proxy server is used for the web, then it is an HTTP proxy. However there may be proxy servers for each application protocol (FTP, ...).
The operating principle of a proxy
The basic operating principle of a proxy server is quite simple: it is a server "mandated" by an application to query the Internet in its place. Thus, when a user connects to the Internet using a client application configured to use a proxy server, it will connect first to the proxy server and give him his request. The proxy server will then connect to the server that the client application tries to join and to transmit the request.
The server will then give its response to the proxy, which will in turn forward it to the client application.
The functionality of a proxy server
Now, with the use of TCP / IP within the LAN, the relay role of the proxy is directly provided by gateways and routers. However, proxy servers are still valid with a number of other features.
The cache function
Most proxies thus provide a cache function (in English caching), that is to say the ability to remember (in "cache") pages most often visited by LAN users in order to provide them as quickly as possible. Indeed, computing, the term "cache" means a temporary storage of data (the term "buffer" is also sometimes used).
A proxy server has the ability to hide (a neologism meaning "cache") information is generally called "proxy-cache".
This feature is implemented in some proxy servers allows one hand to reduce the use of bandwidth to the Internet and reduce the time of access to documents for users.
However, to carry out this mission, it is necessary that the proxy regularly compares the data it stores in memory cache with the remote data to ensure that cached data is still valid.
Filtering
Moreover, by using a proxy, it is possible to track connections (English logging or tracking) through the creation of activity logs (logs) in the systematic recording of user requests when their connection requests to the Internet.
It is thus possible to filter connections to the Internet by analyzing a client requests from the other server responses. When the filtering is done by comparing the client request to a list of requests allowed, it is called white list when it comes to a list of banned sites is called blacklist. Finally the analysis of server responses according to a list of criteria (keywords, ...) is called content filtering.
Authentication
To the extent that the proxy is the indispensable medium of internal network users to access external resources, it is sometimes possible to use it to authenticate users, that is to say, ask them to identify with a user name and a password for example. This makes it easy to give access to external resources to only those authorized to do and can save in the access log files identified.
This type of mechanism when implemented obviously raises many problems related to individual liberties and rights of people ...
The reverse-proxy
Called reverse-proxy (in French the term is sometimes used reverse proxy) server proxy-cache "mounted upside down," that is to say a proxy server not allowing users to access the network Internet, but Internet users to access indirectly to some internal servers.
The reverse proxy serves as a relay for Internet users wishing to access an internal website by submitting queries indirectly. With the reverse-proxy, the web server is protected from direct attacks from the outside, thereby enhancing the internal network security. On the other hand, the cache function of reverse-proxy can help relieve the load on the server to which it is intended, this is why such a server is sometimes called "accelerator" (accelerator server).
Finally, thanks to sophisticated algorithms, the reverse proxy can be used to distribute the load by redirecting requests to different servers equivalents and are called load distribution (load balancing in English).
Dangers
| Confidentiality | Since you ask all your pages to the proxy, it can know all the sites you visited. |
| Passwords | Some web sites require passwords. As you go through the proxy, the proxy will know your password (unless you use HTTPS / SSL). |
| Changes | The proxy provides the pages, but it is also possible that the changes on the fly before you give them (this is rare, but possible). |
| Censorship | Some proxy can be configured to censor sites. |
Therefore trust the proxy administrator. You decide if you want to trust the proxy server of your provider. For those companies ... is to see! Experts estimate that 70% of U.S. companies consider employee access to the proxy.
Another danger: transparent proxy
Some ISPs look at what protocols are used and hijack HTTP requests to their proxy servers.
Why do they do that?
This allows for very precise statistics on Internet users' browsing habits, and such information is selling very well marketting companies.
This saves bandwidth to reduce the amount of data received from the Internet.
It has also happened at a supplier that the proxy-cache recompress images with a lower quality to save space.
How to detect a transparent proxy?
Normally, when you connect to a website without a proxy, it should show your IP address (or your gateway).
Just compare your IP address with that seen by the web server. Disable the proxy in your browser, then compare the IP address below with your IP address. If they are different, then it is because your ISP probably uses a transparent proxy! (Or as you go through a gateway / firewall).
(To find your IP address, run winipcfg.exe Windows 95/98/ME or Windows NT/2000/XP ipconfig.exe)
Your IP address is:
Your Hostname is:
