A trojan named DNS Changer that resets the DNS Servers in a PC has prompted the US Goverment to temporarily shutdown the Internet to give time for web users in the US to remove the Trojan manually. Although a Trojan infecting a computer network is not new, its the first time in history that a Government is shutting down the web to remove one. This will affect some 3 million users in the US and more in the rest of the globe. All this means that now a Trojan is a serious business and the stakes are only going to get higher. 

More about DNS Changer.

The Trojan originated from Estonia. DNS Changer changes the DNS Server settings in your PC and redirects your web apps to their own website featuring ads which bring in revenue for them. The individuals who created it have already been arrested by the FBI using "Operation Ghost Click" and the DNS Server have been brought down. Still the malware is still resident in the PC's of many users in the US and this what prompted the US Goverment to shut down the web.

Ubuntu Linux and the Trojan

Its not sure if the Trojan has affected Windows users alone or whether GNU/Linux based PC's were also affected. You can check if your PC is infected with a Trojan just to be on the safe side. If the image is green in color you are almost on the safe side, if its red, it time to get busy.