Windows Sockets is shrunk into Winsock. The Winsock is the top most level in the Windows network. The LSP stands for Layered Service Provider. The Winsock LSP is a code that allows applications stand in between the network calls generated by the application and the Winsock API that talks to the machine hardware.
Winsock are in a sense tools provided in Windows network for applications to communicate with each others across systems. These are sockets that sit on top of the operating system kernel. When an application wants to communicate in the Windows network, it needs to structure the packet and interface with the Winsock API. The Winsock would then transmit the packet out of the system.
Since, the point between Winsock and the application is the lowest point for packet examination, if we can have a solution at this level, we can work wonders in providing network security solutions. The Winsock LSP does just that. Sitting between Winsock and the application, this code can examine all the packets and take actions are required.
When you think about the ability to supervise all the packets, we get into some real interesting features that can be deployed. Examined packets can be dropped, or redirected or sent through depending on the code logic. Thus these Winsock LSPs can be of real good value to users.
Thus using this LSP, we can provide packet blocking, filtering and redirection solutions to the end users. No wonder there are applications using this concept to redirect HTTP requests, scan emails etc. But remember that LSP is not the only approach to do these things, there are other applications itself that can perform these functions and choice between the two approaches needs to be well thought out.
In short, network security is a very important aspect of modern online world. With Winsock LSP there is a very effective and viable option for implementing such solutions.