DNSChanger Trojan is the name of a piece of malware that was discovered in 2008. It had the effect of calling home to a network server that was subsequently taken down by the US government in 2011.
The concept was that computers would rid themselves of the trojan in the course of upgrades and running security programs…which has happened – except on the 300,000 unlucky few….or maybe more. Regardless of the number, any computer that has the code will attempt to connect to the internet in their usual manner and find an error message. The reason is that the DNS server that their computer has been going to for routing onto the world wide internet was set up as a temporary measure by the US FBI.
These FBI computers were only supposed to be online for 120 days, until March 2012, but there were still a million or two computers banging into the system. So an extension was granted by the court…until 9 July 2012.
To check your computer: DNS Changer Check-Up
Krebs mentions this site if you don’t get the Clean sign: Detect | DCWG
See the following article at Krebs on Security for the details: DNSChanger Trojan Still in 12% of Fortune 500 — Krebs on Security
Good luck to us all.