Please see the article "Critical zero-day bug in Internet Explorer under active attack" published by ars technica at
http://arstechnica.com/security/2012/09/critical-zero-day-bug-in-microsoft-internet-explorer/Also expect an out-of-band update from Microsoft to patch this issue in IE7 and IE8. I would suggest that you check daily for outdated programs. For those of you with home computers, I strongly suggest that you run Secunia Personal Software Inspector and update as required. Ensure your anti-virus is up to date.
The disturbing thing about this exploit is that it has the potential to affect several versions of windows. Also disturbing is that exploits in the wild install a root-kit that "had little or no detection by the 34 most widely used antivirus programs". I expect this also to change, so ensure your anti-virus updates get through.