FXP stands for File eXchange Protocol, and is a method of data transfer that allows a user to transfer files from one server to another, without going through the user’s computer or network.
The Good: In essence it is the closest thing to server-to-server transfer without direct access and the ability to initiate a connection directly from a server.
The Bad: Many servers do not support FXP or have it disabled. Furthermore, normal FTP clients often are not designed for it, but there are a few FXP specific clients.
The Ugly: The reason many web hosting provider system administrators disable it is that it can pose a security risk that most admins are not willing to take. It can expose a server to a vulnerability known as FTP bounce, where an attacker gains access to a server through a port opened by an innocent user, utilizing their machine as a conduit.
As a result, it seems as though most web hosts consider the bad to outweigh the good, and FXP is rarely used. Aside from transferring a site from one server to another, there are few reasons for someone with a shared hosting account to need it at all.
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