A proxy server, also known as a "proxy" or "application-level gateway", is a computer that acts as a gateway between a local network (e.g. Learn the basics about proxies, types, how they work, and the cases where you do and absolutely do not want to use an open proxy. In computer networks, a proxy server is a server (a computer system or an application) that acts as an intermediary for requests from clients seeking resources from other servers. Proxies were invented to add structure and encapsulation to distributed systems.Proxy list · Open proxy · Proxy servers · IP address blocking.
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It is commonly used in both commercial and non-commercial organizations especially schools to ensure that Internet usage conforms to acceptable use policy.
A content proxy server definition proxy will often support user authentication to control web access. It also usually produces logs proxy server definition, either to give detailed information about the URLs accessed by specific users, or to monitor bandwidth usage statistics.
Many workplaces, schools and colleges restrict the web sites and online services that are accessible and available in their buildings.
Proxy server - Wikipedia
Governments also censor undesirable content. This is done either with proxy server definition specialized proxy, called a content filter both proxy server definition and free products are availableor by using a cache-extension protocol such as ICAPthat allows plug-in extensions to an open caching architecture.
Websites commonly used by students to circumvent filters and access blocked content often include a proxy, from which the user can then access the websites that the filter is trying to block.
Some products have been known to employ content analysis techniques to look for traits commonly used by certain types of content providers.
Assuming the requested URL is acceptable, the content is then fetched proxy server definition the proxy. At this point a dynamic filter may be applied on the return path. For example, JPEG files could be blocked based on fleshtone matches, or language filters could dynamically detect unwanted language.
If the content is rejected then an HTTP fetch error may be returned to the requester. Most web filtering companies use an internet-wide crawling robot that assesses the likelihood that a content is a certain type. The resultant database is then corrected by manual labor based proxy server definition complaints or known flaws in the content-matching algorithms.
Some proxies scan outbound content, e.
In a workplace proxy server definition where the client is managed by the organization, trust might be granted to a root certificate whose private proxy server definition is known to the proxy.
Consequently, a root certificate generated by the proxy is installed into the browser CA list by IT staff. The proxy is effectively operating a man-in-the-middle attackallowed by the client's trust of a root certificate the proxy owns.
Bypassing filters and censorship[ edit ] If the destination server filters content based on the origin of the request, the use of a proxy can circumvent this filter. For example, a server using IP -based geolocation to restrict its service to a certain country can be accessed using a proxy located in that country to access the service.
Students can use proxy servers to circumvent this security. However, by connecting to proxy servers, they might be opening themselves up to danger by passing sensitive information such as personal photos and passwords through the proxy server.
Some content filters block proxy servers in order to keep users from using them to bypass the filter. Logging and eavesdropping[ edit ] Proxies can be installed in order to eavesdrop upon the data-flow between client machines and the web.
For this reason, passwords to online services such as webmail and banking should always be exchanged over a cryptographically secured connection, such as SSL.
By chaining proxies which do not reveal data about the original requester, it is possible to obfuscate activities from the eyes of the user's destination.
However, more traces will be left on the intermediate hops, which could be used or offered up to trace the user's activities.
If the policies and administrators of these other proxies are unknown, the user may fall victim to a false sense of security just because those details are out of sight and mind. In proxy server definition is more of an inconvenience than a risk, proxy users may find themselves being blocked from certain Web sites, as numerous forums and Web sites block IP addresses from proxies known to have spammed or trolled the site.
Proxy server definition bouncing can be used to maintain privacy. Improving performance[ edit ] A caching proxy server accelerates service requests by retrieving content saved from a previous request made by the same client or even other clients. Caching proxies keep local copies of frequently requested resources, allowing large organizations to significantly reduce their upstream bandwidth usage and costs, while significantly increasing performance.
Most ISPs and large businesses have a caching proxy.