So what is DSN Changer? For the layman, DNS is a translation service that runs on thousands of servers spread out all over the world. When you navigate to google.com, your browser first checks with a DNS server to translate that human readable google.com into an IP address — 126.96.36.199 in my case — and that address is what the browser actually uses to send it’s request for the page.
The DNS server you’re PC uses is normally set by your ISP automatically, although some advanced users choose to set their DNS themselves for various reasons.
So let’s say you got a virus, and that virus went and changed your DSN settings without your knowledge, what happens next? Since your DNS server address was changed to the bad guys DNS server, he can now give you a bad translation. So the next time you go to google.com, he might actually send you to another server not even owned by Google. He could do this for any website address out there including banks, health providers, the government, etc. You get the concept.
So do your research at www.dcwg.org and run a DNS check to make sure you’re not affected.