The concept of phishing can be summarized as stealing personal and financial users information through false emails. People are generally asked to give some account name and password (which you never should do) by email or through a fake website. According to the Anti-Phishing Working Group (APWG), phishing activities have drastically increased in 2006.
Microsoft is now using data mining to counter this problem (see here for details). The main idea is to build lists of web sites and their correct IP addresses (some other information such as location, internet service provider are also stored). This function will be incorporated in Internet Explorer 6 and 7. The same kind of functionality should be found (or already exists) in Netscape, Firefox and Opera.