Proxy server
A proxy server is called an open proxy if everyone can connect to it and use it. Usually, open proxies are proxy servers which are badly configured. Open proxies may be abused easily; for example, a bad user may send a corrupting request to a remote server, but hide himself behind an open proxy, so the administrators of the remote server cannot stop him. Open proxies can also be used for spamming. For this reason, some websites do not allow connections to their web servers or to edit content on them through known open proxies, including on Wikipedia.