As referenced in the last post we did on this subject, you can visit DNS-Ok.us to to quickly see if you’re infected. Since it’s July 9th today, if you suddenly can’t access the internet, that may be the only red flag you need.
According to PCMag.com, another tool that is available is from Avira, which will tell you if your machine is infected, but is not able to remove the infection. Kaspersky offers a tool that CAN remove DNSChanger.