As per the article :Firefox makes unrequested connections https://support.mozilla.com/en-US/kb/Firefox%20makes%20unrequested%20connections?s=127.0.0.1&r=0&as=s#w_loopback-connection "A loopback connection (to IP address 127.0.0.1) can be made by Firefox on non-Unix machines. In this case the browser is communicating with itself as expected, and it is not recommended that this communication be blocked. " Article above says that "Connection CAN BE MADE by Firefox." 1- Under which conditions this connection can be made? 2- Does Loopback connection made by Web Browser (firefox) creates security hole? 2- Internet Explorer and Google Chrome don't make such a connection, Why does Firefox act like that?