It makes it harder to reveal their identity and thereby helps preserve their perceived security while browsing the web or using other internet services.
Real anonymity and extensive internet security might not be achieved by this measure alone as website operators can use client-side scripts to determine the browser's real IP address and the open proxy may be keeping logs of all connections.
This can result from misconfiguration of proxy software running on the computer, or from infection with malware (viruses, trojans or worms) designed for this purpose.
Because open proxies are often implicated in abuse, a number of methods have been developed to detect them and to refuse service to them.
IRC networks with strict usage policies automatically test client systems for known types of open proxies.