Internet Explorer 6 is still used in many large organisations. It’s because large organisations invest heavily in technology then expect to keep using it for many years to increase their returns on investment. Usually their internal programs won’t work on newer browsers, and it’s a major task to upgrade them.
But Internet Explorer 6 (IE6) is quite old and very vulnerable to being hacked. It’s so vulnerable that it’s the main (technical) cause of the recent hack attack by China against Google (read here). In short, it seems that the Chinese government (or agents working on their behalf) hacked certain people’s Google accounts. They were able to do this because these people weren’t using the latest version of Internet Explorer.
So any organisation that refuses to upgrade to the latest version of Internet Explorer is also at risk.
Microsoft have made an official statement that IE6 is vulnerable and they want everyone to upgrade to the latest version.
Update: The Australian Government has also asked people to stop using IE6.
Update 2: Microsoft has made a patch available to all IE6 users to fix the problem. Download it from here.