HTTP access via proxy server
A proxy server, or proxy for short, is used to allow users within a firewall to access the WWW. A proxy server is a special HTTP server that runs either on the firewall machine or on another Internet-based computer within the firewall.
If a client wants to retrieve a document from the WWW server on the Internet within the firewall, it will contact the proxy server. It accepts the request, forwards it to the server outside the firewall, reads the response of the remote server and then sends it back to the requesting client free proxy.
The proxy server acts as both client and server in this type of communication. Compared to the requesting WWW client, it behaves as a WWW server, compared to the remote server as a client.
The client request header is used by the proxy unmodified for its request to the remote server, which causes the WWW client not to lose functionality when using a proxy server.
Because the WWW supports other Internet services, the proxy server is able to act as a gateway to other information servers such as FTP, Gopher, WAIS or news servers. It shows that the communication between client and proxy is always handled via the HTTP protocol.
The proxy communicates with the remote server via the respective protocol, in this case via the FTP protocol. In addition, the proxy server must convert the objects it receives from the remote servers into HTTP objects before sending them back to the WWW client.
By using a proxy server, access to Internet resources can be controlled and restricted. Access control can be based on access method, IP address, or domain name.
This means, for example, that the proxy server only allows some special computers in the local area network to access the Internet in order to prevent unnecessary costs arising from improper or unintentional use of the Internet.
Code Of The HTTP Transaction
In addition, the WWW access behavior of the local users can be analyzed with the help of a proxy server at the Internet transition. The proxy records client transactions for this purpose. An entry in a log file contains, for example, the IP address of the requesting client, date and time, the URL of the requested object, the size of the transmitted data in bytes and the status code of the HTTP transaction.
In addition to these advantages, the use of a proxy server on the firewall machine also has a major disadvantage.
Since the firewall is the only point of attack of the local network in relation to the Internet, as few security-related applications as possible should run on the firewall in order to minimize any potential security gaps.
Because the more extensive a software is, the more likely it is that it contains errors and thus security holes. For example, if the CERN server is used as a proxy server on the firewall machine, it represents a potential attack target from the outside.