High Quality Content by WIKIPEDIA articles! Layered Service Provider (LSP) is a feature of the Microsoft Windows Winsock 2 Service Provider Interface (SPI). A Layered Service Provider is a DLL that uses Winsock APIs to insert itself into the TCP/IP protocol stack. Once in the stack, a Layered Service Provider can intercept and modify inbound and outbound Internet traffic. It allows processing all the TCP/IP traffic taking place between the Internet and the applications that are accessing the Internet (such as a web browser, the email client, etc.). For example, it could be used by malware to redirect web browers to rogue websites, or to block access to sites like Windows Update. Alternatively, a computer security program could scan network traffic for viruses or other threats. The Winsock Service Provider Interface (SPI) API provides a mechanism for layering providers on top of each other. Winsock LSPs are available for a range of useful purposes, including parental controls and Web content filtering. The parental controls web filter in Windows Vista is an LSP. The layering order of all providers is kept in the Winsock Catalog. Installed LSPs can be viewed using Windows Defender`s Software Explorer or using third-party utilities.