Switching the Microsoft Phishing Filter to automatic makes web browsing (at least firefox) about 5 times slower than usual, taking about 10 sec to start up and display google. When I looked into task manager, McAffee virus scanner was blamed for using 50% CPU time. When either phisihing or McAffee were switched off, everything was fast. I decided against phising. I do not now whether this is enabled by default.