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In HTTP networking, typically on the World Wide Web, referer spoofing (based on a canonised [1] misspelling of "referrer") sends incorrect referer information in an HTTP request in order to prevent a website from obtaining accurate data on the identity of the web page previously visited by the user.
Referer spoofing is typically done for data privacy reasons, in testing, or in order to request information (without genuine authority) which some web servers may only supply in response to requests with specific HTTP referers.
To improve their privacy, individual browser users may replace accurate referer data with inaccurate data, though many simply suppress their browser's sending of any referer data. Sending no referrer information is not technically spoofing, though sometimes also described as such.
In software, systems and networks testing, and sometimes penetration testing, referer spoofing is often just part of a larger procedure of transmitting both accurate and inaccurate as well as expected and unexpected input to the HTTPD system being tested and observing the results. [2]
While many websites are configured to gather referer information and serve different content depending on the referer information obtained, exclusively relying on HTTP referer information for authentication and authorization purposes is not a genuine computer security measure. HTTP referer information is freely alterable and interceptable, and is not a password, though some poorly configured systems treat it as such.
Some websites, especially many image hosting sites, use referer information to secure their materials: only browsers arriving from their web pages are served images. Additionally a site may want users to click through pages with advertisements before directly being able to access a downloadable file – using the referring page or referring site information can help a site redirect unauthorized users to the landing page the site would like to use.
If attackers acquire knowledge of these approved referrers, which is often trivial because many sites follow a common template, [3] they can use that information combined with this to exploit and gain access to the materials.
Spoofing often allows access to a site's content where the site's web server is configured to block browsers that do not send referer headers. Website owners may do this to disallow hotlinking.
It can also be used to defeat referer checking controls that are used to mitigate Cross-Site Request Forgery attacks.
Several software tools exist to facilitate referer spoofing in web browsers. Some are extensions to popular browsers such as Mozilla Firefox or Internet Explorer, which may provide facilities to customise and manage referrer URLs for each website the user visits.
Other tools include proxy servers, to which an individual configures their browser to send all HTTP requests. The proxy then forwards different headers to the intended website, usually removing or modifying the referer header. Such proxies may also present privacy issues for users, as they may log the user's activity.
The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, where hypertext documents include hyperlinks to other resources that the user can easily access, for example by a mouse click or by tapping the screen in a web browser.
In computer networking, a proxy server is a server application that acts as an intermediary between a client requesting a resource and the server providing that resource. It improves privacy, security, and performance in the process.
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Proxomitron, the Universal Web Filter, is a filtering web proxy written by Scott R. Lemmon. This program was originally designed to run under Windows 95. All future development of the program was ceased in 2003 one year before its author's death on 1 May 2004. Proxomitron is still viable and used on later Windows platforms such as Vista and Windows 10.
Various anti-spam techniques are used to prevent email spam.
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URL redirection, also called URL forwarding, is a World Wide Web technique for making a web page available under more than one URL address. When a web browser attempts to open a URL that has been redirected, a page with a different URL is opened. Similarly, domain redirection or domain forwarding is when all pages in a URL domain are redirected to a different domain, as when wikipedia.com and wikipedia.net are automatically redirected to wikipedia.org.
An open proxy is a type of proxy server that is accessible by any Internet user.
The Web Proxy Auto-Discovery (WPAD) Protocol is a method used by clients to locate the URL of a configuration file using DHCP and/or DNS discovery methods. Once detection and download of the configuration file is complete, it can be executed to determine the proxy for a specified URL.
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HTTP cookies are small blocks of data created by a web server while a user is browsing a website and placed on the user's computer or other device by the user's web browser. Cookies are placed on the device used to access a website, and more than one cookie may be placed on a user's device during a session.
In HTTP, "Referer" is an optional HTTP header field that identifies the address of the web page, from which the resource has been requested. By checking the referrer, the server providing the new web page can see where the request originated.
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WebSocket is a computer communications protocol, providing simultaneous two-way communication channels over a single Transmission Control Protocol (TCP) connection. The WebSocket protocol was standardized by the IETF as RFC 6455 in 2011. The current specification allowing web applications to use this protocol is known as WebSockets. It is a living standard maintained by the WHATWG and a successor to The WebSocket API from the W3C.
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A web beacon is a technique used on web pages and email to unobtrusively allow checking that a user has accessed some content. Web beacons are typically used by third parties to monitor the activity of users at a website for the purpose of web analytics or page tagging. They can also be used for email tracking. When implemented using JavaScript, they may be called JavaScript tags.