http://i.gizmodo.com/5183751/giz-explains-how-a-brainy-worm-might-jack-the-worlds-pcs-on-april-1 removal: http://www.symantec.com/business/security_response/writeup.jsp?docid=2009-011316-0247-99
if yahoo found out about it, I'm willing to bet many companies knew about it before. Thats my experience.
I don't think so. Where you download it from has instructions. Just follow them and you should be good.
Microsoft patched this flaw in October. As is usually the case, the danger comes from folks who don't do regular updates. Remember when miamidolphins.com and dolphinstadium.com were infected with Trojans during Super Bowl week two years ago? MS had patched those two flaws 4 months earlier and the admins were simply lax in updating the servers. If you're PC is set to automatically update, you should be fine.
