Web Proxy Autodiscovery Protocol (WPAD)

Last updated: April 25, 2013

What Does Web Proxy Autodiscovery Protocol (WPAD) Mean?

Web Proxy Autodiscovery Protocol (WPAD) is a technique used by client systems to fetch proxy configuration file URLs. WPAD tends to locate the URL of a proxy configuration file using either Dynamic Host Configuration Protocol (DHCP) or DNS. WPAD is responsible for locating the URL, while the web client software interprets the configuration file in regards to the required proxy. WPAD, therefore, can be defined as a protocol for locating the configuration file through DHCP or DNS services.

Techopedia Explains Web Proxy Autodiscovery Protocol (WPAD)

Bandwidth control and restricted privileges for Internet use are key elements of consideration for organizations, Internet service providers and backbone Internet providers. Web proxy and proxy policy configuration has been a technique used to overcome the aforesaid concern since the late 1990s. In the early days, client systems had to be configured manually in regard to proxy settings and configurations. With WAPD, administrators are not required to apply all the proxy-related settings because the configuration file is discovered and downloaded on the client system automatically. It is important to note that each organization has its own proxy mechanism. Netscape designed the initial format of a proxy configuration file and introduced it in 1996 with its Netscape Navigator 2.0 browser. WAPD was drafted by a group of companies like Real Networks, Sun Microsystems and Microsoft Corporation. It was then included in Microsoft Internet Explorer 5.0 for the first time. The documentation of WPAD expired in December 1999, but it is still supported by the major browsers today. It is worth noting that there are two mechanisms for discovering the configuration file. DHCP is the first priority discovery method to fetch the configuration file as compared to DNS. DNS is triggered if the DHCP is unable to locate the configuration file. As soon as the configuration file is discovered by either of the two discovery methods, the file is downloaded and the other method is not performed. However, there are some browsers that support only the DNS method for discovery purposes. Despite WAPD’s numerous advantages, it is vulnerable to attackers and hacking, so it needs to be used with appropriate checks and balances. A malicious user can easily intercept the Internet traffic of the client system by forwarding an altered configuration file. These malicious users can then modify users' Internet browsing and configure their browsers with malicious proxies. Administrators should therefore consider such risks when applying WAPD.

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