What is Microsoft's Phishing Filter? And is it beneficial or a waste to keep turned on?

It seems to make everything run slow when it checks certain sites. It does not always check sites, just once in a while. This may be new, I am running IE with Windows Vista premium home edition.What is Microsoft's Phishing Filter? And is it beneficial or a waste to keep turned on?
It checks sites for information hacks. E.G. there is a site where you have to enter in personal information such as your name and a password which you maybe using in another site such as myspace.com. So it will tell you if there are any information hacks. IF you do enter your pass and name in a site that does phish it will lead to your personal information to be stolen.What is Microsoft's Phishing Filter? And is it beneficial or a waste to keep turned on?
It is a safety feature in IE7 but some people have complained that it does slow things down. You can disable it by going to:



Tools, Internet Options, Advanced



Near the bottom of the list of options, it has a Phishing heading and 3 options. Change it to "Turn off automatic web site checking".