According to the FBI hundreds of thousands of infected PCs could be without Internet access beginning July 9, 2012. The FBI has been planning to shut down a set of servers that were serving ads and other malware-related stuff to computers infected with the DNSChanger trojan virus.
The FBI was able to take control of the servers which have been kept online so that computers still infected with the trojan virus could still connect to the Internet. That may not be the case come July 9th, 2012 since the servers will be disabled. Computers that may still be infected with the trojan may not be able to connect to the Internet.
Good news for people who don't know if they are infected or not. You can check if your PC is one of the infected by going to this website, according to the FBI there were about 350,000 PC’s infected by this virus so it is definitely worth a look to check if your PC is one of those.
Again, click here to check if your PC is infected with the DNS Changer Trojan.
If you prefer to check your DNS setting manually, take a look at this PDF. I decided to not embed the PDF this time.